A STUDY OF THYROID ACTIVITY IN DAIRY CALVES
USING RADIOACTIVE IODINE AS AN INDICATOR

By
James Robert Lodge

AN ABSTRACT
Submitted to the School for Advanced Graduate Studies
of Michigan State University of Agriculture and
Applied Science in partial fulfillment of the
requirements for the degree of

DOCTOR OF PHILOSOPHY

Department of Dairy
1957

Approved

1
ABSTRACT

JAMES ROBERT LODGE

This study was designed to adapt the technique used by
Henneman

(1955) on sheep to the dairy calf and to obtain some

basic information about the normal thyroid activity and secre­
tion rate of the dairy animal.
The rate at which injected 1 ^ 1

was accumulated and excreted

by the thyroid gland and the amount of exogenous thyroxine r e ­
quired to reduce thyroidal i^31 output to a minimum have been
used as indicators of thyroid function in dairy calves.

Radio­

activity of the thyroid was determined by taking external counts
of the gamma radiation over the thyroid region of the neck.
When 30 to 150 /ic of carrier-free 1^31 were injected into

83 calves representing the five dairy breeds, the 48-hour up­
take averaged 36.4 percent of the administered dose.

Brown

Swiss calves generally had a lower uptake than calves of the
other breeds.

The uptake was highest in the summer months and

lowest in the spring months.

Younger calves had a higher up­

take than older calves.
During the declining phase of radioactivity, the 1^31
output from the thyroid was 3.1 percent daily, giving the iso­
tope an apparent biological half-life of 31.3 days.

When thio-

uracil was administered six to twelve days after I^-32- adminis­
tration to prevent further accumulation or recirculation of
1^31, the output rate increased to 13-8 percent daily, and the
biological half-life was reduced to 6.6 days.
The thyroid hormone secretion rate was estimated by the
following procedure:

Daily subcutaneous injections were made

JAMES ROBERT LODGE

ABSTRACT

of purified L-thyroxine with increments added every second
day.

Counts of the radioactivity over the thyroid gland were

taken Immediately prior to the initiation of thyroxine treat­
ment and at the end of the 48 hours after each increase In dose.
The values obtained were calculated as the percent of the pre­
vious count.

The daily dosage required to raise the corrected

external thyroid count to 100 percent, thus producing maximum
inhibition of the gland, was assumed to represent the gland's
normal secretion rate.

Using this technique,

the secretion

rate of 42 calves averaged 0.57 mg. L-thyroxine per 100 pounds
of body weight with a range of 0.38 to 0.84 mg.

Henneman, H. A., E. P. Reineke and S. A. Griffin.
The
thyroid secretion rate of sheep as affected by season, age,
breed, pregnancy, and lactation.
J. Animal S c l . 14:419.

1955 .

A STUDY OF THYROID ACTIVITY IN DAIRY CALVES
USING RADIOACTIVE IODINE AS AN INDICATOR

By
James Robert Lodge

A THESIS

Submitted to the School for Advanced Graduate Studies
of Michigan State University of Agriculture and
Applied Science in partial fulfillment of the
requirements for the degree of

DOCTOR OF PHILOSOPHY

Department of Dairy

1957

ProQuest Number: 10008368

All rights reserved
INFORMATION TO ALL USERS
The quality of this reproduction is dependent upon the quality of the copy submitted.
In the unlikely event that the author did not send a complete manuscript
and there are missing pages, these will be noted. Also, if material had to be removed,
a note will indicate the deletion.

uest
ProQuest 10008368
Published by ProQuest LLC (2016). Copyright of the Dissertation is held by the Author.
All rights reserved.
This work is protected against unauthorized copying under Title 17, United States Code
Microform Edition © ProQuest LLC.
ProQuest LLC.
789 East Eisenhower Parkway
P.O. Box 1346
Ann Arbor, Ml 48106- 1346

ACKNOWLEDGMENTS
The author wishes to express his sincere thanks to Dr.
R. C. Lewis for guidance and help in conducting this study
and for his helpful suggestions in the writing of this thesis.
The interest and helpful suggestions of Dr. S. P. Reineke
during the time this study was in progress were greatly appre­
ciated.

Tiii
i

Also, he wishes to thank him for making available the

and purified L-thyroxine used in this work.
The investigator appreciated the financial support of a

Graduate Research Assistantship provided by Michigan State
University which made it possible for him to continue his
studies and complete this investigation.
He wants to thank Dr. R. F. Elliott, Lederle Laboratories,
Inc.,

Pearl River, New York, for providing the thiouracil used

in this investigation.
Acknowledgment is also due Mr. S. S. Smiley and his
assistants In the barn for their cooperation and for taking
care of the experimental animals.

1

TABLE OF CONTENTS
page
INTRODUCTION

..............................................

REVIEW OF LITERATURE

1

......................................

Economic Aspects of Thyroid Relationships

.........

The effect of the thyroid on milk:
production .....................................
The effect of

the thyroid onreproduction.

.

3
3
3

.

7

The effect of
the thyroid on growth
and fattening...................................

8

Regulation of Thyroid Function......................

9

Methods of Thyroid

S t u d y ........................

17

EXPERIMENTAL PROCEDURE

...................................

26

RESULTS AND DISCUSSION

...................................

28

Trial 1 ..............................................

30

Trial 2 .............

33

Trial 3 ..............................................

35

Trial A ..............................................

38

Trial 5 ..............................................

Ao

Trial 6 ..............................................

A2

Trial 7 ..............................................

A5

Trial 8 ..............................................

A8

Trial 9 ...............................................

A9

General Discussion...................................

50

SUMMARY.....................................................

59

LITERATURE CITED

6l

..........................................

ii

LIST OF TABLES

The effect of thiouracil on the output rate
and biological half-life of i l 3 l ...............
Irregular effect of thiouracil in March,

1955

31
•

34

Estimated thyroxine secretion rate of
calves in May, 1955 .............................

36

Estimated thyroxine secretion rate of
calves in August, 1955 ..........................

40

Effect of single Injections of thyroxine
and estimated thyroxine secretion rates
in normal and ohiourac.il treated calves . . . .

43

Effect of the addition of iodized salt
to the ration on the 48-hour uptake and
on the net output rate of i ! 3 1 ..................

45

Effect of intravenous Injections of
the isotope, I ^ l , on the 48-hour
uptake and on the net output rate .............

47

Estimated thyroxine secretion rate of
dairy calves in May, 1956 ......................

48

Estimated thyroxine secretion rate of
dairy calves in August, 1956. . . . .
.........

49

Effect of season on the 48-hour uptake
of l!3l by the thyroid gland of dairy calves. .

51

Effect of breed on the 48-hour uptake of
ll31 by the thyroid gland of dairy calves

51

.. .

The percent of 24-hour count as a measure
of rate of uptake for the first few hours
after injection of I-*-31 ........................

53

Effect of thiouracil on ll31 output
of the thyroid g l a n d .............................

55

Estimated thyroxine secretion rate
of calves by breed
. . . ......................

57

iii

LIST OP FIGURES
Figure
1.

2.

3.

4.

Page
The 1^31 outpui rate of four heifers.
One
animal appeared to have no output whereas
the others showed a variable rate
between c o u n t s ...................................

29

The effect of administering 0.2 G. of
thiouracil per kg. of body weight, given
in two equal doses daily, on the 1^31
output rate.
The control and experimental
groups consisted of four calves e a c h .............

32

Log of the external thyroid counts of
six calves treated with thiouracil,
followed by thyroxine.
Thiouracil was
administered orally, starting on the
sixth day after I^ol injection.
Thyroxine, In graded doses, was Injected
subcutaneously daily, starting on the
twelfth day with increments added each
second d a y ..........................................

37

Corrected external thyroid counts cal­
culated as the percent of the last pre­
vious count.
The daily amount of thy­
roxine required to raise the percent of
previous count to 100 was assumed
to represent the daily secretion rate
of the thyroid g l a n d ...............................

39

iv

INTRODUCTION
The thyroid gland is interrelated physiologically with a l ­
most every organ and tissue in the body.

Therefore, a deficien­

cy or an oversupply of its hormone may be reflected in demon­
strable changes in many organs and functional processes of the
body.
In recent years, research in the field of thyroid physiology
has been given an added stimulus by the development of methods
whereby thyroid function can be regulated with relative ease.
Not only is this fact of clinical importance, but also it has
been found that artificially Induced hypothyroidism and hyper­
thyroidism affect the productive processes of livestock.
example,

For

the administration of thyroldally active substances

to cows causes an Increase in milk and milk-fat production.
On the other hand, a hypothyroid condition brought about by
the administration of certain goitrogenic agents,

such as thio­

uracil, has been found to enhance the fattening of swine, fowl,
and other domestic animals.
To administer these compounds effectively,

it is first

necessary tohave a clear picture of the normal thyroid activity.
For example, to administer thyroprotein to an animal most effec­
tively, it is essential to know the normal state of activity
of the thyroid gland under given physiological and environmental
conditions.

Otherwise, one might easily give too much or too

little of the hormone,

since the physiological dosage range of

so potent a substance is necessarily short.
1

Until recently, however, an accurate,

comprehensive study

of the normal rate of thyroid secretion has been impossible in
larger animals because of the lack of a suitable technique.
This study was designed to adapt the technique used by
Henneman

(1955) on sheep to the dairy calf and to obtain some

basic information about the normal thyroid activity and secre­
tion rate of the dairy a n i m a l .

By knowing the normal secretion

rates of the young dairy animal, and knowing the correlation
between this secretion rate and the animal's producing ability,
it may be possible to use this technique as a tool in selecting
the animals with a higher production potential at a young age.
Also, by knowing what the normal secretion rate is for high
producing animals, It may be possible,

through stimulation of

the animals' own glands or by feeding hormonal material,
increase the production of low producing animals.

to

REVIEW OP LITERATURE
There is a voluminous amount of material which has been
published on thyroid activity, and this review does not attempt
to cover all of it, but only that part which the author feels
is closely related to this study.
Although early physiological studies had made it apparent
that the thyroid gland produced a hormonal substance, it was
not until Bauman

(1896 ) discovered the presence of iodine in

the gland that great strides were made In the isolation and
Identification of this hormone.

Kendall

(I91A) first accom­

plished the isolation of crystalline thyroxine from thyroid
tissue.

However, it was not until Harington

(1926 ) improved

the technique of extraction of thyroxine that a sufficient
quantity of material was obtained to determine the empirical
and structural formula.

A year later, thyroxine was synthe­

sized by Harington and Barger

(1927 ).

Economic Aspects of Thyroid Relationships
The effect of the thyroid on milk: production.

It is a

well known fact that the use of thyroidal materials will
increase milk and milk-fat production.
Graham (193^&) showed a definite relationship between milk
secretion and the thyroid.

He found it was hard to distinguish

the drop in milk secretion following thyroidectomy from that
accompanying control operations.
3

However, the addition of

4
small amounts of thyroid to the diet of either thyroidectomized or normal cows, during the declining phase of lactation,
caused a rapid rise in milk and milk-fat production.
reported

He also

(1934b) that thyroxine was the principle in the thy­

roid gland which caused the marked Increase in milk-fat pro­
duction.

It was also observed that the rise in milk-fat pro­

duction was always marked, but the rise in milk secretion
showed large variations.

These observations have been confirmed

by a number of workers, including Jack and Bechdel
Herman, Graham, and Turner
Reineke

(1935),

(1938), and Ralston et al

(1940).

(1942) was the first to report on the use of

iodinated protein in cattle.

When this material was fed to

a three-year-old thyroidectomized Jersey heifer, it stimulated
increases in metabolism twenty to thirty percent.

The increased

metabolism was accompanied by an improvement In the appearance
and vigor and the initiation of estrous cycles.

Increases

were noted in the milk yield, milk-fat percentage, and yield
of butterfat of lactating cows after feeding Iodinated protein
for a three day period.
Results of practical trials of feeding synthetic thyroprotein were reported by Reineke

(19^3).

The thyroprotein

was supplied to a number of farmers to find out the effect
under applied conditions.

All cows were in the declining

stage of lactation when feeding started.

Out of 27 cows,

23 showed increases in milk production from 6.6 percent to
60.8 percent after six days or more of feeding.
four cows showed no change in production.

The other

The cows were fed

thyroprotein continuously for periods ranging up to three

5
months.

After one to two months of elevated production,

the

normal decline of lactation occurred, but at a retarded rate
as compared to the n o r m a l .
Since this initial work showing increased milk and milkfat production from using thyroidally active materials,

several

long term studies have been conducted and a great many papers
have been published on the effect of such materials on the
composition of milk.
There is a lot of variation in the reports of the effect
on the composition of milk.

Archibald

(19^5) reported very

little, if any, change in total solids, ash, and lactose and
a decrease in casein.

In contrast to this report, other

workers, including Ralstonet al

(19^+0), have found an Increase

in the percentage of lactose and total solids.
McNaught and Owen

Chanda,

(1952a) also found a small Increase in the

lactose content of milk in thyroxine treated cows corresponding
to a simultaneous decrease in the chloride content.
These workers also found that the calcium, sodium,

potassium,

magnesium, protein, creatine, and riboflavin contents of the
milk were not demonstrably affected by thyroxine treatment.
Chanda et al

(1952b) reported that the calcium content of the

milk was unaffected, as well as the sodium,

potassium, and

magnesium.
Comparatively little work has been carried out on the
effect of using thyroidally active materials on the vitamin
content of the milk.
conclusive.

Some of the work is conflicting and not

It has been shown by VanLandingham et al

and Chanda et al

(1944)

(1952b) that the ascorbic acid content of the

6
milk is decreased by one-fourth to one-third.

Kemmerer et al

(19^-6) has reported no change in the thiamine content, a d e ­
crease in riboflavin and an increase in nicotinic acid.
In a review article, Blaxter et al

(1949) stated "as far

as milk composition is concerned, the milk produced by cows
receiving iodinated casein is perfectly safe and nutritionally
adequate.

The fall in vitamin C content is not of great

importance as far as human consumption is concerned, for milk
is not a major source of the ascorbic acid needed by the human."
Thomas and Moore

(1953) reported on an experiment in which

thyroprotein was fed for approximately 300 days of each lactation
for the length of time that the cows remained in the herd.

Of

the twenty cows receiving thyroprotein in their first lactation,
three cows completed their sixth lactation.
maintained under identical conditions.

Control cows were

Cows receiving thyro­

protein did not leave the herd any quicker than did control
cows.
Thyroprotein caused an immediate increase in the level
of milk production and in butterfat test in practically all
animals.

The feeding of extra nutrients to a level of 125

percent of Morrison's maximum TDN requirement was found to
help sustain these increases.

The feeding of thyroprotein and

extra nutrients did not result in the production of a greater
amount of milk over an entire lactation than in comparable
cows fed extra nutrients only.

The fat test and the mature

equivalent fat-corrected-milk production of cows fed thyro­
protein through several lactations were lower during the second
and later lactations than the corresponding values for the

7
first lactation.

It was also observed that the cows fed

thyroprotein decreased in their efficiency of converting
energy into milk in subsequent lactations, whereas this effi­
ciency remained constant in the control cows.

Also, the

mortality rate of calves born to cows fed thyroprotein under
the conditions of this experiment was higher than for other
calves.
The effect of the thyroid on reproduction.

Little is

actually known about the effect of thyroid secretion on
reproduction of the dairy animal.
Brody and Frankenbach

It has been reported by

(1942) that the thyroidectomized cow

shows a complete absence of normal estruai behavior.

Ovulation

and a normal ovarian cycle occurs and conception, followed
by a normal pregnancy, can occur.
It has been shown by Spielman et al
and Turner

(1945) and by Reineke

(1941), respectively, that the fetal thyroid hor ­

mone can pass the placental barrier in cows and goats.

There

is no reason to believe the reverse can not be true, and, if
this is the case, the continued feeding of thyroactive material
could have an adverse effect on the fetal thyroid gland.
has been reported by Schultze and Turner

It

(1945) that goitrogens

administered to the goat passed through the placenta and re­
sulted in fetal thyroid glands ten times the normal size.
Petersen et al

(1941) found that thyroidectomy of a bull

resulted in complete clinical myxedema, leading to a disap­
pearance of libido and interest in the estruai female.

Sperm­

atogenesis was apparently not affected since ejaculates ob­
tained by ampullae massaging were normal in sperm activity,

8
morphology,

longevity, and fertilizing ability.

Libido was

completely restored upon the administration of thyroidal mate­
rial.

(19^ 6 ),

Iodinated casein, fed to 1^ aged bulls by Reineke

produced favorable results in that ten of them showed increased
vigor and a more speedy ejaculation.
The effect of the thyroid on growth and fattening.

Thy roid-

ectomy depresses the growth of all animals and this effect in
cattle has been reported by Brody and Frankenbach
Spielman et al

(19^5)•

(1 9 ^ ) and

The latter authors also stated that

growth depression was much more apparent in the young ruminant
than in older animals.
and Turner

The above workers, as well as Reineke

(19^1)> have shown that growth is completely

restored by the injection of thyroxine or by feeding thyroid
material or iodinated casein.
Brody and Frankenbach

(1 9 ^ )

found a 60 percent depression

in growth of a thyroidectomized Jersey calf which was not
observed in 13 and 15 month old calves by Spielman and his
co-workers

(19^5).

Blaxter et al

(19^9) suggested in their review that induced

hypothyroidism by goitrogens to increase fat deposition prior
to marketing calves or older animals might have some economic
value.
Very little work has been conducted on the effect of mild
hyperthyroidism on growth.

With the levels used in producing

an increase in milk production, there has generally been a
loss in body weight by the animals under treatment.
Nevens, and Gardner

Millen,

(19^8) found a slight increase in growth

above normal controls when two dairy calves were given 1.3

9
grams of iodinated casein per 100 pounds of body weight.
When four grams per 100 pounds of body weight were fed to two
dairy calves, symptoms of extreme hyperthyroidism occurred.

Regulation of Thyroid Function

Marine

(1935) noted that the thyroid gland is endowed with

tremendous capacities for increasing or decreasing its functional
activity as indicated by changes in weight, microscopic appear­
ance, iodine content, and blood supply.

Also,

studies on the

mitotic activity of the secreting cells of the thyroid, iodine
content of the blood, histological appearance of the gland
including the presence or lack of colloid in the gland, and
changes of the basal metabolic rate

(B.M.R.) all have indicated

that the secretory activity of the thyroid is influenced by
changing environment.
To interpret the meaning of such changes in the thyroid,
an understanding of the normal regulatory mechanism is essen­
tial.

The primary regulatory mechanism controlling the activ­

ity of the thyroid has been revealed by experimental work with­
in the past thirty years.

Such work shows that the anterior

pituitary secretes a thyrotropic factor that regulates thyroid
activity.

Foster and Smith (1926) found that the B.M.R. was

markedly lowered in rats by hypophysectomy and could be brought
back to normal by pituitary implants or thyroid administration,
thus showing a relationship between the anterior pituitary
and the thyroid.

Keating et al

(19^5) showed that, upon

thyroid hypertrophy in the chick, there was a rapid loss of
iodine stores from the gland, indicating a high degree of

10
thyroid activity.
Further evidence of the control of the thyroid gland by
the anterior pituitary has been shown through radioactive
iodine studies,

Randall and Albert

(1951) found that hypo-

physectomy greatly decreased iodine uptake in the rat, and
Fredrickson, Ganong, and Hume

(1955) found a significant

depression of uptake at all time intervals in the hypophysectomized dog.

The latter workers also found a much lower

blood clearance rate of 1^31 ±n hypophysectorn!zed dogs compared to
normal dogs.

They also showed that, when thyrotropin was

administered before tracer injection, the initial uptake of
radioactive iodine was greater than normal and it reached a
maximum earlier than in dogs not receiving thyrotropin.
Morton and his associates

(19^2) suggested that hypophy-

sectomy did not severely interfere with the conversion of
iodide to dliodotyrosine but the overall conversion of iodide
to thyroxine was limited.

Keating et al

(19^5) presented

data showing that thyrotropic stimulation produced a prompt
and early acceleration in the rate with which radioactive
iodine previously stored in the thyroid was lost from it.
From their work they concluded that the thyrotropic factor
seemed to operate primarily as a stimulus for release of thyroid
hormone into the blood stream upon a relatively sudden need
for it by the body.
to the action,

That nervous connections are not necessary

since hypertrophy of the thyroid appears to

occur in autotransplants, was shown by
haus

(1936) .

Salmon

and Sevring-

11
Reforzo-Membrives

(19^3) showed that thyroid hormone Itself

has a depressing effect on the release of thyrotropic hormone.
There exists a normal balance,

therefore, between the thyroid

by way of its hormone and the anterior pituitary by way of its
thyrotropic factor.
There are a number of factors which can shift this balance,
resulting in a gland which is highly active or a gland with
very little activity.

Some of these factors act upon the ante­

rior pituitary, changing its production of thyrotropic hormone,
whereas others act directly on the thyroid gland.

Among the

agents acting through the anterior pituitary are temperature,
light, and nutrition.

Some of the factors acting directly on

the thyroid gland are insufficient iodine intake and drugs,
such as thiouracil, which prevent the formation of thyroid
hormone and cause a goitrogenic effect.

This goitrogenic effect

is due to an increased output of thyrotropic hormone caused
by an insufficient amount of circulating thyroid hormone.
Many studies have been conducted to show the effect of season
and temperature.

Seiden

and Fenger (1913) showed that the

thyroid of sheep, hogs and cattle had a maximum iodine content
in the late summer and a minimum iodine content in the late
winter.

Kendall and Simonsen

(1928) confirmed and extended these

observations by showing that more of a thyroxine-like fraction
is contained in the thyroid of mammals in midsummer than in
F eb ru ar y.
In fowl, an opposite relationship apparently exists.
Cruickshank

(1929) found a higher thyroid iodine content in the

winter months and a lower content in the summer months.

This

12
discrepancy between mammals and fowl can be explained on the
basis that little storage of colloid takes place in the fowl
thyroid during the summer such as apparently occurs in the
thyroid of the mammal.
It has been established that low temperature will stimulate
the thyroid to increased activity.

Dempsey and Astwood

(1943)

found that the thyroid gland of rats produced thyroid hormone
at a rate of 9*5 ^ thyroxine per day when kept at a temperature
of one degree Centigrade.
Centigrade,

At a temperature of 35 degrees

the daily secretion rate was 1.7^ thyroxine.

Reineke and Turner

(1945) found the highest secretion rate of

young chicks in the winter and the lowest in the summer.
Turner

(1948) also showed a decline in thyroid secretion rate of

White Leghorn hens between January and May.
Leblond et al

(1944) showed that when rats were kept in a

zero to two degree Centigrade temperature for 26 days, the
glands fixed 2.7 times more radioiodine than controls kept at

25 degrees Centigrade.

This greater fixation of radioiodine

was not definite until after seven days and was absent after
forty days of exposure.

A diminished thyroid activity was ob­

served as early as one day and persisted for 26 days when rats
were exposed to a temperature of 32-34 degrees Centigrade.
A daily thyroxine secretion of 0.04 mg. in July was sig­
nificantly lower than in any other month when determinations
were made in sheep by Henneman et al
Blincoe and Brody

(1955).

(1955a) found that increasing the ambient

temperature above the comfort zone to 35 degrees Centigrade
decreased the thyroid activity 30 to 60 percent in the four

13
breeds of cows studied.

Holstein cows showed the greatest

decrease and Brahman the least.

Decreasing the ambient temper­

ature below the comfort zone to -8 degrees Centigrade increased
the thyroid activity 60 to 100 percent in Jersey and Brahman
but not in Holstein or Brown Swiss cows.

Air velocity in the

range of 0.5 to 10 m.p.h. had no effect on the thyroid activity
of the four breeds of cows.

The addition of radiant energy

(light) reduced the thyroid activity of Jersey and Holstein
cows but did not affect Brahman cows.

Starvation for four

days markedly reduced the thyroid activity of Holstein cows.
Another publication by the same authors

(1955b) showed similar

results in thyroid activity in Jersey and Holstein cows from
temperatures above and below the comfort zone.
Puntriano and Meites

(1951) found that continuous light

induced significant reductions in thyroid weight, thyroid
reaction to thiouracil and thyroid uptake of radioactive iodine,
whereas continuous darkness had the opposite effect in mice.
It was concluded that continuous light depresses while contin­
uous darkness Increases thyroid secretion in mice.
It was shown by Mulinos and Pomerantz

(19^0) that a poor

nutritive condition depresses thyroid activity in comparison
to a good nutritive condition.
The role of iodine and its effect on thyroid activity is
very well demonstrated by its goitrogenicity in humans and,
although not as noticeable in domestic animals, can be ob­
served In the hairless^ pig and large necked calf when iodine
is deficient.

Many foods produce a goitrogenic effect which

can be remedied by Increasing the amount of iodine in the diet.

14
Among these are soybeans, alfalfa, and cabbage.
However, there are certain classes of compounds which,
when fed, cause a goitrogenic condition that cannot be reme­
died by even relatively large intakes of iodine.

MacKenzie,

Mackenzie, and McCollum (1941) observed that rats on a diet
containing sulfaguanidine had markedly enlarged thyroids com­
pared with those of controls.

Histologically the thyroids

showed marked hyperplasia, the epithelium was distinctly colum­
nar and was so increased and invaginated as to nearly extinguish
the lumen.

Richter and Clisby (1941) observed that administering

phenylthiourea caused thyroid hypertrophy.

Kennedy and Purves

(1941) found that a diet containing Brassica seed caused a
goitrogenic effect which was only partially prevented by iodine
administration.

MacKenzie and MacKenzie

(1943 )» in extending

their studies, found that many of the sulfonamides had a goitro­
genic effect on the thyroid.

Astwood

(1943) made a detailed

study of the goitrogenic action of many compounds and found
that the most active compounds were substances having the
thioureylene radical

(NH*CS*NH).

Thiourea and most of the

derivatives were found to be very active although the deriva­
tives were more toxic.

Thiouracil is active and of low toxicity.

Whereas most of the above work was accomplished with rats,
Mixner, Reineke, and Turner

(1944), using chicks, also found

an enlargement of the thyroid when thiouracil was used and
suggested that the method might be used as an assay procedure
for thyroxine secretion rate.
The authors investigating the effects of these goitrogenic
agents

(MacKenzies, 1943* and Astwood et al, 1943) report that

15
the thyroid's histological picture indicates hyperactivity,
such as a much increased acinar tissue with increased height
of the epithelial cells, a greatly reduced colloid, increased
size and number of follicles and
Although the enlargement and

hyperemia.
histological picture of

the

thyroid induced by the drugs indicates a hyperactive gland,
studies of their indirect effects on physiological processes
indicate hypofunction of the thyroid.
Astwood et al

The MacKenzies

(19^3 )> and Reineke, Mixner and Turner

(19^3),
(19^5)

all have observed a depression of the basal metabolic rate of
animals given these drugs.
The exact mechanism of action of these goitrogenic drugs
has not been definitely determined, but

it is generally believed

to be due to interference in an enzyme system that is involved
in the synthesis of the thyroid hormone.
Although excessive intake of iodine has been repeatedly
shown to not prevent the goitrogenic effect of these drugs,
Astwood et al

(19^3) and MacKenzie and MacKenzie

(19^3) showed

that the injection of preformed thyroxine does prevent the
thyroid hypertrophy when given during the treatment with the
drugs.
Based on the above observations, Dempsey and Astwood

(19^3)

conceived the idea of using thiouracil treatment simultaneously
with thyroxine injections as a method of determining the
thyroid's secretion rate.
Perlman, Morton and Chaikoff

(19^1* 19^2 ), employing tracer

amounts of radioactive iodine without carrier, conducted a
series of studies on the distribution of various fractions

16
of thyroid iodine under different experimental conditions.
They have reported that, as the time interval after administering
tracer iodine Increases,

there is a concomitant increase in the

proportion of labelled iodine in the thyroxine-like fraction.
These same investigators and Anderson

(19^2) found that, though

the thyroids of hypophysectomized rats collect much less of the
tracer iodine than do the thyroids of intact animals, the amount
collected is real and measureable.

As reported earlier, the

iodine is readily converted into the diiodotyrosine-like frac­
tion but very little of the tracer is demonstrable in the
thyroxine-like fraction.
Morton and his associates

(19^3) also studied the formation

of thyroxine and diiodotyrosine by completely thyroidectomized
animals.

They reported that totally thyroidectomized rats

are able to convert iodide to diiodotyrosine and thyroxine.
By in vitro techniques

(19^)

they demonstrated that various

sulfonamides inhibit the formation of diiodotyrosine and
thyroxine without affecting the concentrating power of the
thyroid slices.

In another in vitro study ( 1 9^ )

they found

that the addition of a small excess of iodide to each flask
Inhibits the conversion of inorganic iodine to diiodotyrosinelike and thyroxine-like iodine.
Using the same in vitro techniques, this group of investi­
gators

(i944) studied the effect of goitrogenic substances on

the conversion of iodine by sheep thyroid slices.

They found

that thiourea and thlouracil strongly inhibit the formation
of diiodotyrosine and thyroxine but do not prevent the col­
lection of inorganic iodide.

Potassium thiocyanate was found

17
not only to depress the conversion of inorganic iodine but also
to prevent the collection of iodine by thyroid slices.
This group of workers

(19^4) also studied the influence

of thiouracil on the formation of thyroxine and diiodotyrosine
by the intact thyroid gland of the rat.

The feeding of thio­

uracil for seven days depressed the uptake of radioactive iodine.
The thyroid of rats receiving thiouracil contained only about
half the amount of radio-thyroxine and about one-third the
amount of radio-dliodotyrosine found in the normal glands.

Methods of Thyroid Study
Magnus-Levy

(1895) administered thyroid material to a

normal individual and found a marked increase in oxygen con­
sumption and carbon dioxide output.

From this observation

arose the most widely used method of studying thyroid activity.
It is still used in diagnosing thyroid disorders in humans,
although in the past few years the use of radioactive iodine
as a diagnostic tool has gained much prominence.

This method

has also been widely used in laboratory animals as an assay
procedure for thyroxine.
loses its usefulness.

However, in the large ruminant, it

For an accurate determination of the

basal metabolic rate, the individual or animal must be In a
fasted, rested,

subdued state.

It is very difficult to keep

large animals in a subdued state and almost Impossible to
obtain a fasted ruminant animal.
from the gases in the rumen.

Further complications arise

In measuring the carbon dioxide

produced, not only is that produced by metabolism of the body
measured but also that produced by bacterial fermentation in

18
In the rumen.

The other gases produced In the rumen also inter­

fere in this determination.
The loss in body weight of animals and restoration of growth
in thyroidectomized animals have been used in studying thyroid ally active mat er ia ls .

However,

these methods are only quali­

tative and not sensitive enough for quantitative measurements.
The discovery of goitrogenic compounds, referred to earlier,
made possible a new type of thyroid study based on maintenance
of the hormone balance between the thyroid and pituitary glands.
The method involves the use of a goitrogenic agent such as
thiourea or thiouracil that has a thyroidectomy effect and
results in thyroid enlargement.

By the subcutaneous injection

of graded dosages of thyroxine, the weight of the thyroid is
reduced in thiouracil- or thiourea-treated animals and the
weight reduction in general is proportbnal to the thyroxine
dosage.

Thus, the establishment of a normal thyroxine-thyro­

tropin equilibrium by injection of thyroxine in thiouraciltreated animals results in a thyroid weight equal to that in
control animals.

The quantity of thyroxine required to bring

about this result is considered to be an estimate of the normal
thyroid secretion rate by the glands of a particular group
of animals.
Dempsey and Astwood

(19^3) &re given credit for proposing

this method and using it to determine the secretion rate of
rats.

Reineke, Mixner and Turner

(19^5) found that values

obtained by this goitrogenic method compared very well with
those from basal metabolic rate measurements.

Many workers

have used this technique in the study of thyroid activity and

19

the factors affecting the activity.
knowledge

Undoubtedly, most of the

gained about the thyroid secretion rate of different

animals today has been obtained by this method.

However, this

method does not readily lend itself to the study of thyroid
activity in the large domestic animal,

such as the dairy cow,

due to the fact that the animals need to be sacrificed to ob­
tain the results.
A method which has been used in larger animals with some
degree of success has been the protein-bound-iodine method,
better known as the FBI method.

Curtis et al

(1933) reviewed

the early results of blood iodine determinations in humans
which established the relation between the level of blood iodine
and thyroid status.

He concluded that there is good agreement

between the blood iodine level and thyroid function.
further study, It was found by Turner et al
and his workers

Upon

(19^0) and Salter

(1941) that the total blood Iodine failed to

reflect the actual thyroid status under all circumstances.
Clark and Boyd

(19*10) were unable to show any seasonal variation

in thyroid activity of pigeons and chickens through the blood
iodine, even though it is known that such a variation does
exist.
Because of these findings, workers turned to using the
protein-bound-iodine fraction of the plasma,
Long and co-workers

serum, or blood.

(1951) found significant differences in

protein-bound-iodine content of serum between breeds of dairy
cattle.

Reece and Man

(1952) have presented evidence of a

nonthyroidal iodine fraction in the plasma protein-bound-iodine
of cattle.

20

In a review, R a pport and

Curtis

(1950)

state that the

level of bo th the FBI and Inorganic Iodine is demonst rably
affec te d by iodine in an y form and that this is its chief
disadvantage.
Le wis

(1952),

in an extensive

study in dairy cattle,

ob­

served no effect when cows which had not

previously received

iodized

However,

salt were

supplemented with it.

he also stated

that the amou nt of iodine in the supplemented diet may have
been no mor e than ad equa te and,

if the supplemental iodine had

been In excess of the a n i m a l s ' needs,

the results might have

been different.
Since the d i s cove ry of artificial r a d io ac tivit y by Joliot
and Curie

(193*0* a ne w er>a ^ as developed In the study of

metabolic

processes.

As M a rine

(1915) demonstrated,

the thyroid gland is unique

In that It has the abilit y to collect iodine selectively In
r e l a t i v e l y large quantities.

It Is,

therefore, not surprising

that studies with the ra dioacti ve isotopes of Iodine have proved
r e adi ly ap p l i c a b l e In the study of thyroid

physiology.

Five Isotop es of ra dioactive iodine have been described
in detail by Livingood and Seaborg
ra dio active iodine was
on iodine.
minutes,

(1938).

The first avail able

prepared by the action of slow neutrons

Its atomic weight is 128 and its half life Is 25

whic h limits its usefulness in biological

studies.

B o m b a r d m e n t of Iodine with fast neutrons gives rise to a r a d i o ­
active element wh ich has a half life of 13 days and atomic weight
of 126.

A n o t h e r ra dioactive Isotope of Iodine,

having a half

life of four days and an atomic weight of 12-4-, arises from the

21

b o m b a r d m e n t of a n t i m o n y with, h e l i u m i o n s .

The bo mbardme nt of

me tall ic

te l l u r i u m gives rise to two ra dioactiv e isotopes of

iodine.

One has a hal f life of 12.5 hours and an atomic weight

of 130.

The other has a half life of 8 days and an atomic

we ight of 131*

This last is the one in most common use today

and its eight day half life makes it very convenient for use
in b i o l og ical exp erimentation.
H e r t z and his as soci at es

(1938,

19^0,

19^1) were the first

to f o ll ow the dis tr ib u t i o n of radlo lod ine within the body after
its a d m i n i s t r a t i o n

for the purpose of obtaining information

co nc ern in g thyroid

function.

the normal

These workers demonstrated

that

thyroid collects far greater amounts of administered

labelled iodine than do other tissues.

The normal

thyroid of

rabbits was found to collect up to eighty times the quantity
to be expected
tissues.

from uniform diffusion into the general body

They also found that a gland,

the thyrotropic hormone,
the q u a n t i t y expected
strated

collected up to several hundred

from uniform diffusion.

that the thyroid of animals

iodine collects

made hyperplastic with

They also d e m o n ­

previously treated with

smaller amounts of the administered tracer

iodine than does the thyroid of normal animals.
from com pa ri ng thyroid iodine collection,
re la tive thyroid

times

They concluded

acinar cell height,

size, and basal metabolic rate that the result

of thyrotropic hormo ne Injections may be regarded as an initial
stimulation,

followed by an involution,

istered,

functional depr ess ion after prolonged thyrotropic

and

stimulation.

if iodine is a d m i n ­

22

C h a i k o f f and his as so ci a t e s
act ive

(19^3,

1944)

utilized r a d i o ­

iodine for the study of Iodine m e t a b o l i s m with in vitro

techniques.

The y Incubated

thyroid slices in R i n g e r ’s solution

con t a i n i n g tracer amou nt s of ra di oac tive iodine and
mined the fract ion s of Inorganic,

then d e t e r ­

dii odo tyro si ne -l ike and th y ­

r o x i n e-li ke rad ioacti ve iodine in the thyroid tissue.

They

found that slices of thyroid from dogs and sheep convert less
iodine into organic

fractions than do those from rats.

Ha m i l t o n and Sole y

(1938,

1939*

19^0) were the first to

report the use of radi oac tive isotopes in tracing the course
of iodine given to human beings.

They compared the uptake of

labelled iodine by the thyroid of normal controls with that
of patients wi t h various thyroid diseases.

These measurements

were made by placing a Geiger counter tube over the isthmus
of the thyroid gland and mea suri ng the gamma rays emitted from
the r a d i o ac ti ve iodine that had been collected in the thyroid.
Werner,

Q u i m b y and Schmidt

(1949)

used the 24 hour uptake

of r adioa ct iv e iodine as the most stable time at which to
as s a y thyroid function in humans.

The uptake by the euthyroid

gland has leveled off, as has that by the gland in h y p e r t h y ­
roidism,
period

at that time.

Moreover,

measurements at the 24 hour

provide a range of normal uptake which separates the

great m a j o r i t y of patients with h yper th yr oi dism and h y p o t h y ­
r o i d i s m from those with normal function.
(1 9 5 0 ) det er mined

These same workers

from the 24 ho ur uptake that there was no

st a ti st ic al ly si gn ificant effect of season on average uptake
by euthy roid Individuals.

They also found a slight but

pr o­

g r e ss ive de cre as e in uptake with each decade in age and that

23

women had a sl i g h t l y hi gh er ave rage uptake than men.
W e r n e r et al

(1 9 5 0 ) compared the tracer technique with

the basal met ab ol ic rate d e t er minat io n and with the serum
p re cip it abl e iodine determi nati on.
three m e tho ds in diagnostic

They found errors in all

studies.

However,

the tracer

technique gave a smaller percentage of error than did the
basal met a b o l i c rate determination.

The y found by combining

two or mor e of these tests a high degree of accurac y in d i a g ­
nosis was obtained.
Morton,

Perlman and Cha ikof f

(1941)

afte r labelled iodine was injected,

found that,

two hours

four to nine percent of it

was found deposite d in the whole of the thyroid gland removed
from each of the normal or control guinea pigs, whereas 12 to

23 percent was taken up by the glands that had been made h y p e r ­
active by thyrotropic hormone treatment.

At the 26 hour i n t e r ­

the whole normal glands contained from 14 to 27 percent

val,

of the a d mini st er ed

labelled iodine and the hyperactive glands,

from 32 to 4l percent.

In both cases,

however,

the major

portion of the labelled iodine held by the glands was not
free but ap p r o x i m a t e l y 90 percent of it was organically bound.
There are a n um be r of ways by which factors can be shown
to influence the release of iodine from the thyroid gland.
Wo lff

(1951),

using the biolo gic al half-life as a measure,

found it to be 3.3 days in control rats.
percent

Rats rec eiving 0.03

p ro py lthi our acil in their diet had an ac celerated r e ­

lease w it h a hal f- lif e of 1.6 days.

Hypo ph ysec to my resulted

in a h a l f -lif e of 24 days which was returned to normal in 24
hours by thyrot ropin treatment.

Treat ment with 15><g

thyroxine

2k
daily had an effect

similar to h y p o p h y s e c t o m y .

sence of propylthiouracil,
half-life

thyroxine

prolonged

of l 1 3l in the thyroid to 26 days.

In the pr e­
the biological

Controls receiving

an e q ui va le nt amo un t of iodide had a 1.4 d a y half-life.
the a b s e n c e of propylthiouracil,

In

the thyroxine and control

va lue s were 24 and 3*7 days respectively.

Thyrotropin t r e a t ­

ment m a r k e d l y acce le ra te d the release of I 1^1 from the thyroid.
In addition,

It was de monstr ate d

showed a latent

that the actio n of thyrotropin

period of two to three hours before any si gni­

ficant effect could be shown on I -*-31 release.

He also found

that large doses of Iodide failed to Influence the release of
p re vio us ly injected 1^31 from the gland.
Al b e r t and T e n n e y

(1951),

using the method

of a p ro po r­

tional rate of di sa pp ear anc e of thyroidal 1^31 as percent per
day,

found that thiouracil accelerated thyroidal

fold,

thyroxine inhibited the release,

and

secretion six

sodium Iodide i n ­

duced either no change or a depr ess ion of secretory rate.
P er ry

(1951)

proposed a method

for measuri ng thyroid hormone

secretion in the rat and suggested its use as an assay procedure
on thyroid extracts.

B y mea su ri ng the rate of loss of r a d i o ­

act ive iodine from the thyroid gland of the rat, an
the secretion of thyroid hormone may be obtained.

index of
The validity

of this index has been suggested by the effect of such influences
as thyro trop ic hormone,

thiouracil,

thiocyanate,

and thyroxine.

It has been found that secretion is marked ly inhibited by the
a d m i n i s t r a t i o n of quanti ties

of thyroxine of the order of 10 -ug*

Wi t h lower doses of thyroxine,

a rel ati on sh ip be tween dose and

degree of in hi biti on of thyroid hormone may be demonstrated.

25

Based

on these facts, a rapid and simple

b i o a s s a y of thyroid

procedure for the

preparations was proposed.

F r o m Perry's work,

He n n e m a n et al

(1952) reported the d e v e l ­

opment of a m e t ho d for q u a n tit at iv el y mea sur ing the thyroid
secr eti on rate of Individ ua l intact

sheep.

The

procedure i n t r o ­

duced by these aut hors involves direct counts of ra dioactiv ity
in the thyroid r e gi on to determine the amount of thyroxine
that mus t be given da ily to suppress the output of previously
collected 1^31 fj»om the g l a n d .

The method was confirmed and

extended b y exper im ent s in rats

(Reineke and Singh,

It has been used by He nne ma n et al

1954).

(1955) and Singh et al

(1954)

to study some of the environmental and

physiological factors

related

These findings were the

to thyroid function in sheep.

basis for the method used in this study.
A met ho d reported by Pipes and Ruppert
and T u r n e r

(1955) differed from the above In that radioac tiv ity

counts were taken on samples of blood
over the thyroid.

plasma Instead of directly

It has the disadv ant age of being considerably

more tedious to apply.
of l!3l

(1955) and Pipes

Adm in is tr ation of sufficient quantities

to insure satisfactory counting levels in blood

also in tro duces

plasma

serious danger of thyroid Injury in the animals

through excessive radiation.
workers have since changed
as rep or te d by Pipes,

It might be added that these

to the met ho d employed In this study

Premachandra and Turner

(1956).

EXPERIMENTAL PROCEDURE
The experi me ntal anim al s were from the Michiga n State U n i ­
ve r s i t y d a i r y herd and Included the Jersey,
B r o w n Swiss, and Ay r s h i r e breeds.

Guernsey,

The average age was 5.2 months

with a standard de via ti on of 2.2 months.

The calves received the

re g u l a r calf ratio ns used at the University.
iments

Holstein,

In the early e x p e r ­

the rati on did not include supplemental iodine.

for the later experiments,

However,

the ration was supplemented with

iodine at the level re co mmended to dairy farmers.
A tracer dose of carrier-free 1^31,

up to 150 juc, was i n ­

jected either sub cu ta ne ously or In tr av enous ly Into each heifer.
The uptake of 1^31 by the thyroid gland was followed by taking
counts

of the r a d i o a c t i v i t y from the thyroid area of the neck

at hourly,
sible,

daily,

or alternat e day intervals.

As far as

pos­

the same amoun t of pressure was applied on the nec k of

the calf each time the counts were taken.
the ca lc ulatio ns

was the max im um repeatable count obtained

from this re gi on of the neck.
b ac kg round and the
source was used

The count used in

All counts were corrected for

physical decay of the isotope.

A Co^

to standardize the instruments.

D u r i n g the earlier studies, a shielded end -window T G C -8
G e i g e r - M u e l l e r Tube
count rat e me t e r

(Tracerlab) was used v/ith a model l6l5B

(Nuclear).

1620 count rate me t e r
Once

A scintillation counter and model

(Nuclear) were used for the later work.

the slope of the output curve was established,

thyroxine,

purified b y repeated recrystallizations,

26

L-

was admin-

27
istered d a i l y b y su bc utaneous injection.
r e c r y s t a l l i z e d and fur nished b y Dr. E.

The thyroxine was

P. Reineke from the

P h y s i o l o g y D e p a r t m e n t of M i c hi ga n State University.
stalline

The c r y ­

thyr oxi ne was weighed and then dissolved in a dilute

Na o H solution.

En o u g h HC1 was added to make the solution

slightly c l o u d y befo re it was diluted with distilled water to
obt ai n the desire d concentration.
roxine for a few days use was
kept under refrigerati on.

Only enough of the L-thy-

put into solution, and this was

The dosages were started at a low

level and inc re me nt s were added each second day.
of each

At the end

period of a given thyroxine level, an external thyroid

count was taken.

In this way,

the effect of each increment

upon the rate of 1^31 output b y the thyroid was determined.
The thyroxine

secretion rate was estimated by plotting

each corrected thyroid count,
of the last

previous count,

calculated as the percentage

against the thyroxine dosage.

The a m o u n t of thyroxine required
vious count to 100,

to raise the percent of pre­

or to produce a leveling off of il31 o u t ­

put to a m i n i m u m rate,

was considered to represent the normal

secretion rate of the thyroid g l a n d .

RE S U L T S AN D DISC US SION

Pr el i m i n a r y trials were conducted In order that the author
could gain experie nce in the countin g technique and in handling
isotopes.

Fr om these early trials,

it was found that the t h y ­

roid gland

of d a i r y calves collected a substantial amount of

the i n j ec te d r a d i o a c t i v e iodine in a rel at iv ely short
of time, but that the output was very slow.

period

The biological

ha lf -l ife was In the neighborho od of twenty days.

Since a t ­

tempts

to me asu re the thyroxine secretion rate of the calves

in the

prelim in ar y experiments were unsuccessful due to the slow

rate at which the 1^31 was eliminated from the thyroid of the
experi me ntal animals,
techn iqu e

some adj us tm en t had to be made in the

pre viously employed.

the counts were so erratic
a valid output rate.

In addition,

it was found that

that it was impossible to establish

Figure 1 Illustrates this situation.

A r e a s o na bl e explan at ion for the appar ent lack or irregularity
of 1^31 output seemed to be that the iodine was salvaged from
the m e t a b ol iz ed hormone and recycled

through the gland.

In earlier work by Lewis and Re ine ke

(unpublished),

had be en found that oral dosag es of 50 mg.
given da i l y or on alter na te days did not

it

of sodium iodide

prevent the apparent

r ec i r c u l a t i o n even when the treatment was continued for one to
two w e e k s .
Af t e r this
rected

pr eli minary work, a number of trials were d i ­

toward d e t e r m i n i n g the rate and degree of uptake by the

thyroid gland and
calves.

the thyroid

secretion rate of a number of

These trials will be reported and discussed individually.

28

count

29

2

-

Log

of corrected

external

thyroid

2 0 II

2

4

6

8

Days after I

Figure 1.

10

12

14

16

131 administration

The I3^ 1 output rate of four heifers.
One animal
appeared to have no output whereas the others showed
a variable rate between counts.

30
Trial

Ei g h t calves
shires)

l

(two Holsteins,

were gi ven

four Jerseys, and two Ayr-

subcutaneous inj ections of 150

F o r t y - e i g h t hours after the injection,

m g

counts were taken over

the thyroid gland area of the neck, and

the percent of the

injected dose taken up by the thyroid was calculated.
permit c o m p ari so n of the relative

of I 1^1 .

To

percent of the I 1 ^ 1 that

was co lle ct ed by the thyroid, aliquots of the injection s o l u ­
tion were counted in a ’’phantom n e c k , ” similar to that d e ­
scribed by B l i n c o e
the

(1953)*

This method was used in determ ini ng

percent of iodine uptake by the calves in this trial and

all subsequent

trials.

The percentage of the 48-hour uptake of

these calves can be found in Table I.
Since thi ouracil is known to prevent
iodine into thyroxine,
of this dru g would

incorporation of

it was thought that the adm in ist ration

prevent the recycling.

strated b y G o l d sm it h et al

It had been d e m o n ­

(1 9 5 1 ) that compounds related to

thiouracil Increased the excretion rate of a tracer dose of
ra d i o a c t i v e iodine from the human thyroid gland.
observa ti on was made by Wo l f
Singh

(1955) repor ted

mal and

(1951)

In rats.

similar thyroid

Reineke and

secretion rates in n o r ­

t h i o ur acil-t re at ed rats.

A level of 0.2 g.

thiouracil

per kilogr am of body weight

daily was used in this trial because,
trials,

This same

in the preliminary

an oral dose of 0.1 g. of thiouracil was not effective

in preventi ng the rec irculation.

Ely et al

(1948) reported

that 0.2 g., adm i n i s t e r e d in divided doses at 12-hour intervals,

31
TABLE I
THE E F F E C T OF TH I O U R A C I L ON THE OUTPUT RATE
A N D B I O L O G I C A L HAL F- LI FE OF 1*31
Ca l f
No.

Age

Breed

48 Hr.
Uptake

wt.

(mo s.)

(lbs.)

w

Daily Output Biol HalfRate1
Life2
1-12
12-18
1-12
12-18
(days)

(*)

26l

A

6.5

380

49.0

4.3

3.1

1
—1
•
VO

22 .4

590

H

5.5

340

51.0

1.3

2.3

53.3

30.1

114-3

J

10.0

465

37.9

4.7

12 .1

14.7

5.7

1145

J

8.5

400

33.9

4.3

7.7

16.1

9.0

262 T

A

6.0

355

35.9

1.1

12 .3

63.0

5.6

59 iT

H

5.5

330

53.0

0.8

21.3

86.6

3.3

1144*

J

9.0

408

39.8

4.0

28.6

17.3

2A

ll46T

J

7.0

300

48.4

6.7

36.7

10.3

1.9

X
/W f
t
.f
t
.
£

w W

V
f
tW

* « w

'

V

— ——

——

— — —

'
—

J

= i L ^ log ^
x 1 0 0 , where -fi = daily output rate
in percent, t= experimental time in days, AT- count
at end of experimental time, AO - count at start.

2 B i o l o gi ca l half-lif e calculated from the formula,
T 1/2 = jr^gg
T Thioura cil tre atment 12 to 18 days
e f fec ti ve ly mai ntai ne d a re l a t i v e l y h igh concentration of
thiouracil in the blood of calves.
Four of the calves receive d thiouracil by capsule starting
on the twelft h d a y after the Injection of the isotope.
of the da ily dosage was given in the morning and
was g iven a p p r o x i m a t e l y twelve hours later.
calves were used as controls.
th iour ac il

Half

the remainder

The other four

The effect of this level of

on the output of I ^ 1 Is dem on strated in Figure 2.

32

I
Control

x
9

Thiouracil \

TJ

9

U

fc
9

I -

9

°

8

7

6

-

-

6

8

10

Oays after I

Figure 2.

12

131

14

16

18

20

j

administration

The effect of ad mi ni st ering 0.2 g. of thiouracil
per kg. of body weight, given in two equal doses
daily, on the 1^31 output rate.
The control and
experimental groups consisted of four calves each.

The r e s u l t s of thioura cil tre at me nt on da ily output rate and
b i o l o g i c a l h a l f - l i f e are

shown in Table I.

r e a d i l y that the level of thiouracil
tively incre ased

It can be seen

used in this trial e f f e c ­

the net output of 1^31 #

W h e n it had become obvious that the detectable output
was g r e a t l y i n c r ease d by thiouracil treatment,
injected

s u b c ut an eo us ly at the rate of 1 mg.

thyroxine was

per 100 pounds

of b o d y w eight to all calves daily for a period of three to
four days.

Ev en though the injection

counts on the calves were ve ry low,

period was short and the

it was demonstrated that

thy roxine did decrease the rate at which the I -*-31 w a s eliminated.
Trial 2

In the mo n t h of March,
Jerseys,

eight calves

and four Br o w n Swiss)

with 1 5 0 >uc of I -*-31.
II), and,

two

were injected subcutaneously

The 48-hour uptake was determined

(Table

on the fourth day after Injection of the isotope,

all calves were

started on thiouracil at the level found to be

ef fective In the previous trial.
uracil

(two Holsteins,

The same effect from the t h i o ­

treatment was not observed in all the calves that had

bee n seen in the previous trial.

This lack of effect from the

thiouracil will be discussed further in a later trial.
In this

par ticular trial,

the supply of thiouracil which

was b e i n g used was exhausted on the sixth day and a supply of
m e t h y l t h i o u r a c i l which was several years old was substituted.
Several

of the calves which did not show a good response to the

thi ouracil
0.4 g.

were given increased amoun ts to a level of 0.3 or

per ki logr am of bod y weight.

Wh e n a new supply of

34
TABLE II
I R R E G U L A R EFF EC T OF TH I O U R A C I L IN MARCH,
Calf
No.

Age

wt.

48-hour
Uptake

(mo s.)

(lbs^

(*)

Br ee d

1955

Daily
Output
Rate

Biol.
Halflife
(days)

w

594

H

3.0

205

37.5

5.0

13.9

595

H

2.0

168

52.7

13.3

5.2

1149

J

3.0

140

50.6

5.7

12.2

1150

J

2.0

91

20.3

3.4

3025

BS

3.5

235

42.5

1.5

46.2

3026

BS

3.0

200

30.1

8.9

7.8

302 9

BS

2 .0

265

4i.i

3.5

19.8

3030

.B S

1 .0

130

18.1

5.3

13.1

*

* Count was above the count rate meter range.
thiouracil was received,
kilogram.

the level was reduced to 0.2 g.

The hi gh er levels of methylthiouracil appeared

have no effect on the output rate but did, however,
a p p a r e n t adverse effect on some of the calves.
3 02 9 had

per

to be removed

to

have an

Calf number

from the experiment because of a bad

cold and ge nerall y run-dow n condition.
T h y ro xine was ad mi ni st er ed In graded dosages to those
calves which did
rates

show a cc ep ta bl e output rates.

used were 0.1,

0.3,

100 pounds of bo d y weight.

0.6,

0.9, and 1.2 mg.

The dosage
thyroxine

B e ca us e of the relative lack of

effect i v e n e s s of thiouracil In this trial, no actual
tion rates were estimated.

However,

It appeared

m a x i m u m i n h i bi ti on of the thyroid gland
to 0.9 mg.

per 100 pounds.

per

s ec re ­

that the

occurred between 0.3

Trial 3
In May,

one Holstein,

two Jerseys,

B r o w n Swiss cal ves were injected
of I 1 -*1 .

one Guernsey,

and four

subcuta neo usly with 135 yuc

The 4 8 -h our uptake of the I 1^! was ag ain determined

and can be found in Table III.

The uptakes are conside rably

lower th an those r e po rted in the previous trials.
uptake will be di sc us se d in more detail later,

This lower

but unseasonably

w a r m w e at her was noted during the 48 hours of the uptake

phase,

w hi ch might have had an influence upon the amount of iodine
col lected by the glands.
On the sixth da y af ter injection,
of 0.2 g.
calves.
ment,

per k i log ra m of body weight,

thiouracil,

at the level

was started on all eight

Af t e r two counts were obtained on the thiouracil tr e a t ­

it was observed that the treatment was effective in

i n c r e a s i n g the output of 1^-31 from the glands of the calves.
The count fr om most of the calves was between 70 and 80 percent
of the previous count,

which the aut ho r feels is a sufficient

output to permit obtai ning secretion rate values.
T hy ro xi ne inj ection s were started after the second count,
ten days af ter Inj ection of the isotope.
to all calves at a level of 0.3 mg.
weight.

ThiB level

of thyroxine had

r es pon se

on the calves used

Thyroxine was given

per 100 pounds of body
shown very little,

previously and was the basis for

st art ing the calves on this level.

The plan had been to Increase

the level of thyroxine by increm en ts of 0.1 mg.
day,

but,

throu gh an error,

stead of 0.4 mg.

If any,

every second

the second level was 0.6 mg.

in­

The increm en ts ther eaf ter were 0.1 mg. as

36
TABLE III
E S T I M A T E D T H Y R O X I N E SEC R ET IO N RATE
OF CALVES IN MAY, 1955

No.

Ca lf
Br e e d

Age

(rnos .)

wt.

48-hour
U ptake

(lbs.)

(*)

D ai ly
Output
Rate

w

Biol?
Halflife

Est.
Thy .
Seer.
Rate

(days)

(mg/100#)

592

H

5.5

395

25.5

7.5

9.2

0.75

1147

J

7.5

315

18.9

13.5

5.1

0.78

1148

J

6.5

320

17.5

18.4

3.8

2022

G

7.0

355

29.4

4.7

14.7

0.77

3023

BS

6.5

395

20.5

8.6

8.1

0.84

3024

BS

5.5

410

26.3

10.5

6 .6

0.51

3027

BS

4.0

415

15.2

13.3

5.2

0.73

3028

BS

4.0

290

11.9

4.3

16 .1

0.64

* The bi olo gical half -l ife was calculated for the per­
iod of time when the calves were under thiouracil
treatment.
planned

until

the end of the experiment.

Thyroxine was i n j e c t ­

ed once each day at a p p r ox im at ely the same time.
animals receiv ed

Thus,

the

two injections at each level of thyroxine,

and thyroid counts were taken at the end of each period.
results of this trial can be found in Table III.

The

As is shown,

secretion rates were obtained on seven of the eight calves.
Calf n u m b e r 1148 had
the count bec ame

to be dropped from the experiment because

too low due to a re latively low uptake and

a h i g h output rate.
F ig ur e 3 shows the counts obtained from six of the calves
d ur in g this trial.

These values give typical curves

produced

37

Thiourocit
Thyroxin*

X

V

Doys o ft*r I 191 odministrotion

Figure 3.

Log of the external thyroid counts of six calves
treated with, thiouracil followed by thyroxine.
Thiouracil was administered orally starting on the
sixth day after I131 injection.
Thyroxine, in
graded doses, was injected subcutaneously daily
starting on the twelfth day with increments added
each second day.

38
by cal ve s

under the tr eatment employed.

d osag e was

pr o g r e s s i v e l y increased,

As the thyroxine

its in hi bit ory effect upon

the thyroid gland was marked by a decreased rate of I-^l o u t ­
put.

The thyroxine

each thyroid
a g ain st

count,

secretion rate was estimated by plotting
expressed as the percent of previous count,

thy r ox in e dosage

r e qui re d

(Figure 4).

to ra ise this figure

as the an imal 's

th yroxine

The amount of thyroxine

to 100 percent has been taken

secretion rate.

It also was found

that whe n the thyroid gland was co mp let ely inhibited,
whe n the

percent of previous count reached 100,

any ad di ti o n a l

that is,

the effect of

incr eases in thyroxine was unpredictable.

was a l s o noted by H e n ne ma n et al

(1955)

This

in sheep.

Trial 4

Two Holsteins,
were injecte d

three Jerseysand

three Br own Swiss heifers

sub cut an eo us ly with 30 uc of i ^ 31 in August.

The 48 - h o u r counts were obtained and the uptake calculated as
previously.

A scintilla tion counter was used

r e m a i n d e r of the counts and in all

for obtaining the

subsequent trials.

The same

procedure was followed as in the previous trial in that t h i o ­
uracil,

at 0.2 g.

all calves

per kil og ra m of bo dy weight,

was started on

six days a f t e r the injection of the isotope.

to an a p p ar en t delayed

effect of thiouracil,

Je r s e y calves were started on 0.3 mg.
pounds of b o d y weight

only the three

of thyroxine

per da y on the tenth day.

were g i v e n inject ion s of 0.4 mg.

per 100

All calves

thyroxine on the twelfth day

and were continued on increm ent s as has been explained
viously .

Due

pr e­

39

3028

count

3027
3023

Percent of previous

3024

/
1147/2 02 2 /

70

Mg. I-th y ro x in e odministered per IOO lbs.

Figure 4.

Corrected external thyroid counts calculated as
the percent of the last previous count.
The daily
amount of thyroxine required to raise the percent
of previous count to 100 was assumed to represent
the daily secretion rate of the thyroid gland.

40
TABLE IV
E S T I M A T E D T HY R O X I N E SE CRE TIO N RATE
OF C AL VE S IN AUGUST, 1955
Ca lf
Age
No.

Wt.

48-hour
Uptake

Daily
Output
Ra te

Breed
(mos.) (lbs.)

(*)

(%)

Biol.
Halflife*

Est.
Thyroid
Sec .
Rate

(days) (mg.A 00#)

596

H

5.0

335

59.3

15.5

4.5

0.57

598

H

4.5

295

70.3

9.2

7.5

0.53

1151

J

5.0

245

80.8

24.0

2.9

0.47

1152

J

4.5

220

70.8

30.4

2.3

0.52

1153

J

4.5

26 0

59.3

26.3

2.6

0.57

3031

BS

5.5

405

67.2

27.3

2.5

0.60

3032

BS

5.0

350

65.6

19.1

3.6

0.54

3033

BS

3.5

2-50

44.5

11.6

6.0

0.56

* The bi ol ogi cal half-life was calculated for the
period of time when the calves were under thiouracil
treatment.
The re sul ts of this trial are found in Table IV.

The

a v e r a g e thyr oxi ne secretion rate obtained in this trial was
somewhat lower than that found In the previous trial.
probably due to a temperature effect,

This is

since it is assumed that

the thyroid a c t i v i t y is de pressed during hot weather.
Trial 5
In this trial,

12

and four B r o w n Swiss)
juc of I 1 3 1 .

calves

(four Guernseys,

were Injected

four Jerseys

subcutaneously with 50

A f t e r the 48-hour uptake was determined,

the

calves were d i vi ded Into four groups with one calf of each of

41
the three b re ed s in each group.

Since it has only been assumed

that the e ff ec ti ve length of time of a single dose of thyroxine
is 24 h ours or less,

this trial was designed to determine the

le ngt h of time a single dose of thyroxine is effective in normal
and t h i o u r a c i l - t r e a t e d calves.

It was also designed to evaluate

the p o s s i b i l i t y of a cumula tiv e effect of thyroxine a d m i n i s t r a ­
tion as well as

to obtain mea su rem ents of thyroxine secretion

rates of nor ma l and thiouracil-t rea ted calves.
The first g r o u p of three calves was to receive only single
i nj ec tions of t hyr oxine with counts obtained daily to determine
the l ength of time a single dose is effective.
rate of I ^ l

was

The output

so si0w and variable from day to day that no

thyroxine was ad m i n i s t e r e d until the 22nd day after the injection
of the isotope.
roxine

At that time, a single dose of 0.1 mg.

per 100 pounds of body weight was administered.

of the d a i l y var ia tio ns found before the injection,
of this dosage,
The
on the

if any,

th y ­
Because

the effect

was not clear.

second gr o u p of three calves was started on thiouracil

sixth d a y afte r injection of the isotope and on the

twelfth da y a single injection of 0.6 mg.
pounds of bo d y weight was given.

thyroxine

per 100

The output of 1*31 was slowed

in two of the three an ima ls with the effect lasting not more
than two days.

However,

on the fo ur th day.
mg.

of thyroxi ne

the 20th day.

a n e w red uction in output was observed

A similar effect was also noted after 0.3

per 100 pounds of body weight was injected on

No ex pla nati on can be given for the delayed

effect.
The calves in g ro up three were treated the same as those

K2
in g r o u p one except that a dosage of 0.3 mg.

thyroxine per

100 pounds of b o d y weight was given on the 22nd day with the
idea of o b t a i n i n g the thyroid

secretion rates of the calves.

The r e s u l t s of this d osag e were no more distinguishable than
in the first group.
The thyroxine

secretion rates of the calves in the fourth

gr o u p wer e obtained in the man ner established in the previous
trial.
The re sults

of this trial can be found in Table V, and

further effects of thiouracil on the output rate of 1^31 can
be noted.

It al so confirms the need for thiouracil treatment in

o b t ai ning thyroxine

secretion rates of dairy calves.

The

length of time that a single dose of thyroxine is effective
could no t be established,

but,

gr ou p r e c e i v i n g thiouracil,

from the indication found in the

further work: should be conducted

along this line.
Trial 6
Since Mi ch igan lies in a goitrogenic area and the rations
did no t include a n y supplemental iodine,

it was thought that

the a d d i t i o n of iodine in the ration might influence the uptake
and output of I 1^ 1 .
con t a i n i n g 0.02

On the first of December,

percent

were injected

salt

potassium iodide was mixed in the c o n ­

centrate rati on at the recomm end ed
Prior to this trial,

iodized

two calves

level of one percent.

(one Guernsey and one Ayrshire)

su bc ut aneou sl y with 50 /ac of I ^ ^ »

were calc ul ated as usual and were found

The uptakes

to be no lower than

the up takes of calves the previous year which is reported in

TABLE V
E F F E C T OF SI NGL E INJECTIONS OF THYROXINE
A N D E S T I M A T E D TH YR OX IN E SE CRETION RATES
IN N O R M A L A N D TH I O U R A C I L TREATED CALVES
Ca l f
No .

Age

wt.

48-hou r
Uptake

(lbs.)

(%)

Breed
(mo s.)

Daily
Output
Rate

Biol.
Halflife
(days)

Est.
Thyroid
Sec .
Rate
(mg/ 100#)

Gr o u p 1 - No Thi ouracil
1151
2023
3033

J
G
BS

310
425
390

6.5
8.5
5.0

36.4

3.4

20.4

35.3
21.8

2.9
4.6

23.9
15.1

28.0
31.2
28.6

10.5
12.2
11.3

6.6
5.7
6.1

2.3
4.5
3.6

30.1
15.4
19.3

16.8
16.9
19.6

4.1
4.1
3.5

Gr ou p 2 - Thiouracil

1150
2024

J
G

1153

J

425

8.5
7.5
6.0

455
365

Gr oup 3 - No Thiouracil
1152
2026
3030

J
G
BS

6 .0
4.0
8.0

300
270
500

33.3
46.8 24.9

Gr o u p 4 - Thiouracil
3032
2027
3031

BS
G
BS

Table I.

465
260
520

6.5
3.5
7.0

26.0
74.5
27.5

The uptake of one calf could not be calculated

48 hours be ca us e
rate m e t e r or,

at

the count was beyond the range of the count

in other words,

in excess of 60 percent.

other cal f had an uptake of 49.2

The

percent of the injected dose.

Counts were obtained every second day for 30 days.
culated

0.41
0.53
0.36

The c a l ­

percent of da ily output rate was 1.9 and 0.8 percent,

which gives a calcul ate d biolog ical half-life of 36.5 and 86.6
days r e s pect iv el y.

It ap pea red

that,

if the addition of iodized

salt to the r a t i o n had an y effect,
I^~^.

However,

It depressed the output rate

there was a period of appro xima tel y three

weeks in late F e b r u a r y and early Marc h when the iodized
not inclu de d in the rati on

salt wa

so the values obtained on the two

calves m i g h t no t give a true picture.
At the time

this trial was started,

iodized

salt was

placed in the ma ngers of the calves.

Two days later,

it was

in clu ded

(four Jerseys,

two Hol-

in the ration.

steins and

Eight calves

two B r o w n Swiss)

were injected subcutaneously with

50 juc of 1^31 j_n early March.
the iodiz ed

It can defini tely be seen that

salt had no detrimental effect on the uptake when

the val ues obtained in this trial
those of Trial

2

(Table V I ) are compared to

(Table II), which were obtained the previous

year when no iodized

salt was Included in the ration.

It was

pa rt ic ularl y desir ab le to learn if thiouracil administration
would be n e c e s s a r y to obtain a sufficient output rate of the
calves.

It was obvious afte r eight days that the output was

no g r e a t e r than had

previously been found so thiouracil t r e a t ­

ment was

started at the same level as in the previous trials.

The same

procedure was also followed,

thyroxin e was

with the exception that

started at a level of 0.4 mg.

per 100 pounds of

b o d y wei ght r a t h e r than at 0.3 mg. because the counts were
g e t t i n g low by the time the injections of thyroxine were made.
It was concluded
was adde d

from this trial

to the ration,

that,

thiouracil

even though iodized

salt

treatment was still n e c e s ­

sary to remov e va riati on from and to steepen the output curve.

45
TABLE VI
E F F E C T OF TH E A D D I T I O N OF IODIZED SALT TO THE RATION
ON TH E 4 8 -HOUR UPTAKE A N D ON THE
NE T OUT PUT RAT E OF I1 31
Calf
No.

Age

wt.

Br.

4 8 -hr.
Up tak e

Dail y
Output
Rate
Bef.*

(mos.) (lbs.)

(*)

Aft.*

Biol.
Est.
HalfThyroid
life
Sec.
B e f * Aft*
Rate
(days)

(%)

(mg .A 00#)

599

H

7.0

430

31.5

1.5

8.7

46.2

8.0

0.64

600

H

5.0

315

31.1

1.9

8.0

36.5

8.7

0.51

1151

J

12.0

500

3^.7

4.4

8.7

15.8

8.0

0.47

1152

J

11 .0

490

26 .6

1.8

8.7

38.5

8.0

0.51

1154

J

8.0

4io

33.8

4.3

13.0

16.1

5.3

O.oO

1155

J

6.0

275

40.0

2.3

9.6

30.1

7.2

0.60

3034

BS

o.O

385

24.9

1.7

13.1

40.8

5.3

0.62

3037

BS

5.0

310

27.5

1.1

12.2

63.0

5.7

0.49

* Bef.

* B e f o r e thiouracil; Aft.

= Af te r thiouracil

Trial 7
It was thought that intravenous injections of the isotope
mi g h t

possibly have a diffe ren t effect on the uptake and output

rate than was observed

from subcutaneous injections.

(six Ho lsteins and two B r o w n Swiss)
with 5 0 /jlc of I 131 in April.

The calves

were injected intravenously

The injections were made in the

jugular vein and were successful in six of the eight calves.
In the other two calves,

a portion of the I 131 appeared

been dep os it ed in the tissue outside

to have

the vein.

To find if the kind of inj ection would have any effect on
the outp ut rate, no further treatment was given

ohe calves

>46
until

18 days a f t e r the inje cti on of the isotope.

it was
—

1/

o b vio us by this time that the intra ven ous injection was not
g o i n g to incre ase the output rate,
started.

As was found

so thiouracil treatment was

the previous year in the month of March,

thiouracil had an I r r eg ul ar effect on the output rate.

There

is no r e a d i l y a v a i l a b l e explanati on for this lack of effect.
H i g h l e y et al

(1954)

found that the iodine level in the diet

prior to the feeding of thiouracil had a pronounced effect on
the res p o n s e to thiouracil,

in that It exerted its maximum

effect on the thyroid gland

of rats when the iodine level of

the diet was ne ar the mi n i m u m level required to prevent thyroid
e n la rg emen t in the normal rat.
cause in this case

This, however,

could not be the

since it happened when calves were not on

supplemental Iodine as well as when they were.
re spo nse has als o been indicated by Turner

This lack of

(1948) when he was

e v a l ua ti ng the use of the thiouracil-thyroxine method for e s ­
timating the thyroid

secretion rate of White Leghorn hens.

He found that the method was satisfactory for a period in the
fall and wint er whe n thyroid enlargement under the influence
of thiouracil
however,

is at a maximum.

During the spring and summer,

the range of thyroid weight response was too small to

permit one to d is t i n g u i s h any except gross differences in the
thyroidal

potency of test substances.

This lack of response

to thiourac il d ur in g this time needs further Investigation.
S ec re ti on rates could not be obtained for the calves in
this trial be cau se

of the lack of response

The re su lts

seen In Table VII.

can be

to thiouracil.

47
TABLE VII
EFFECT OF I NT RA VE NOUS INJ ECTI ONS OF THE ISOTOPE, I 1 3 1 ,
ON T H E 48- HO UR U PT AK E A N D ON THE NET OUTPUT RATE
Ca lf
No.

Age

Wt.

Breed

48-hr
Uptake

(mo s.) (lbs.)

Daily
Out put
Rate
Bef.*
Aft.*

W

Biol.
Halflife
Bef.*
Aft .*
(day s)

(*)

601

H

6.0

380

24 .7

0.7

602

H

6 .0

376

19*5

2.3

603

H

6.0

330

3 1 .2

0.6

7.4

116.5

9.4

505

H

4.0

290

53.5

1.4

5.8

49.5

11.9

6o5

H

4.0

245

43.2

1.1

607

H

3.0

185

39.0

3039

BS

5.0

300

21.2

3.3

3040

BS

4.0

275

29.9

1.5

in the inorganic
output.

form,

17.8

30.1

6 3 .O
9.0

7.7

= Bef or e thiouracil;

It was thought that the I ^ l

99.0

21 .0
2.8
Aft.

CM

* Bef.

3.9

24.8

= After thiouracil

in the gland was possibly

since thiouracil did not increase its

T h ioc ya na te has been shown to cause the release of

inorganic

iodine from the thyroid gland.

of this trial,

potassium thiocyanate,

per pound of body weight,
of the calves,
had not.

At the termination

at a level of 10 mg.

was injected intravenously in two

of which one had received thiouracil and one

There was no change in the radioactivity from the

thyroid regio n during a five hour period after injection of the
thiocyanate.
Iodine
cyanate

This would Indicate

present.

However,

that there was no inorganic

the effective dosage level of th i o—

for da iry calves is unknown,

have bee n too low.

so the level used may

43
Trial 8
In May,

eight calves

(three Jerseys, three Brown Swiss

and two Holsteins) were Injected intra ven ously with 33 /ic of
131
I
. The main purpose of this trial was to obtain the t h y ­
roxine

secret io n rate of the heifers.

The usual

procedure

was followed i n c l u d i n g the determina tio n of the 48-hour uptake,
the a d m i n i s t r a t i o n of thiouracil
the injection,

and graded doses of thyroxine given on the tenth

day a f t e r injection.
trial,

and

started the sixth day after

No th in g unusual was observed in this

the results may be found in Table VIII.

TABLE VIII
E S T I M A T E D THYROXINE SECRETION RATE
OP DAIRY CALVES IN MAY, 1956
Calf
No.

4 8 -hr.
Uptake

Age

Wt.

(mo s.)

(lbs.)

w

Breed

Daily
Output
Rate*

Biol.
Halflife *

w

(days)

Est.
Thyroid
Sec .
Rate
(mg/100#)

608

H

3.0

200

40.4

4.4

15.8

0.62

809

H

2.0

180

36.9

7.9

8.8

0.53

1157

J

4.0

'15

24.8

5.0

13.9

O .56

1158

J

4.0

170

32.4

8.3

8.3

0.54

1159

J

3.0

120

19-8

14.7

4.7

0.55

3041

BS

4.0

240

14 .9

5.3

13.1

0.37

3042

BS

4.0

270

14 .6

8.5

8.2

0.49

3043

BS

4.0

250

30.3

4. 6

15.1

0.38

* Calcul ate d for the period of time when the calves
were under thiouracil treatment.

49

Trial 9
This

trial was co ndu ct ed in the same manner as the pre­

vious one and was des igne d

primarily to obtain secretion rates

of the eigh t calves injected.
Holstein,

two B r o w n Swiss,

m

this trial in August,

two Jersey and two Guernsey heifers

were in je ct ed I n t r a v e n o u s l y with 50 uc of i 13 l .
and th yr oxine

two

treatm ents were

Thiouracil

started as usual with the ex c e p ­

tion of one J e rs ey calf, which appeared to have a fairly steep
and con s i s t e n t output rate.

The thyroxine

secretion rate of

this calf was de te rmi ned without the use of thiouracil.
result,

The

w hi ch can be found in Table IX, was very similar to

that found

from the other calves.

TABLE IX
E S T I M A T E D THYROXINE SECRETION RATE
OP DAIRY CALVES IN AUGUST, 1956
Calf
No .

Age

wt.

(tnosj

(lb s.)

48-hr.
Uptake

B re ed

Daily
Output
Ratea

Biol.
Halflife3
(days)

(*)

Est.
Thyroid
Sec .
Rate
(mg.AOO#)

610

H

5.0

250

2 9 .O

8.8

7.9

0.62

612

H

5.0

265

30.2

10.4

6.7

0.65

lloO

J

5.0

210

b

32.1

2.2

0.57

1161

J

5.0

215

b

12.4C

5 .6G

0.57°

2033

G

5.0

175

9.3

7.5

0.59

2034

G

4.0

180

b

19.0

3.6

0.65

304'+

BS

5.0

235

33.1

13.9

5.0

0.57

3045

BS

5.0

245

33.6

12 .1

5.7

0.58

b

a C al cu la ted for the period of time when the calves
were under thiouracil treatment.
5 Coun t was above the count rate meter range.
c Ca lf n u m b e r ll6l receiv ed no thiouracil.

50
General Dis cuss io n

As can be noted,

there is conside rabl e variation in the

48-hour uptake wit hi n and between trials.

Although the causes

of these d i f f e r e n c e s have not been co mpletely resolved in this
study,
age.

the ma j o r factors involved appear to be season, breed and
The a v er ag e 48-h our uptake of 83 calves has been 36.4

percent of the injected dose.
in the

The highest uptake has been

summer mont hs and the lowest in the spring months as

seen in Table X.

Wh en compared to conclusions drawn by Seiden

and F e ng er

that the highe st iodine content of cattle

(1913)

thy roi ds was found in the late summer and the mi nim um iodine
conte nt in the late winter,

this difference in uptake thr ough ­

out the year is not too surprising.

Table XI shows the average

4 8- hour uptake of the 83 calves ac cord ing to breed.

The g r e a t ­

est di f f e r e n c e a pp ears to be betwe en the Brown Swiss and the
other

breeds.

The uptake of the Br own Swiss calves averaged

a bo ut 10 percent less than either the Jerseys or the Holsteins.
So fe w A y r s h l r e s and Guernseys were used in this study that
c o m p a ri so ns cannot be made,
In this

study,

it would

but,

from the few that were used

seem that their uptakes are not d i f f e r ­

ent fr om those of the Jerseys

or Holsteins.

There is not a

large d i f f e r e n c e in the 48-hour uptake of the calves of
d i f f er en t ages in this study.

However,

there is an indication

that the y o ung er calves have a higher uptake than the older
ones.

The distr ib u t i o n of the calves in each season, breed

and age c la s s i f i c a t i o n makes It difficult to carry out a st a t i s ­
tical analysis,

but it appe ars that there may be a breed-season

TABLE X
E F F E C T OF SEASON ON THE 4 8 -HOUR UPTAKE OF I 1 ^!
B Y TH E T H Y R O I D GLAND OF DAIRY CALVES
Sea so n

Num ber
of
Animals

48-hour
Uptake

Standard
Deviation

m

Winter
(J a n - M a r )

24

38.4

9-7

Sp rin g
(Apr-June)

24

26.7

10.4

Summer
(July-Sept)

12

53.6

18.5

Fall
(Oct-Dec)

23

35.5

15.5

TABLE XI
E F F E C T OF B R E E D ON THE 48-HOUR UPTAKE OF I 131
B Y THE THYROI D GLAND OF DAIRY CALVES
Br eed

Number
of
Animals

48-hour
U ptake

Standard
Deviation

(*)
3

kk.i

26

29-3

13.8

Gue rns ey

8

38.9

15.7

Ho ls te in

22

37-9

13.6

Je rse y

24

40.9

17.4

83

360

Ay rs hi re
B r o w n Swiss

Overal1

—

i n t e r a c t i o n w h i c h means

that,

when talking about a breed or

season d i f f e r e n c e , one has to specify the particular breed and
season wh i c h is be in g compared.
I

131

The average 48-hour uptake of

by the J er sey calves was higher than that of the Brown

Swiss in the winter,
in the

spring.

summer and fall,

but was about the same

The Ho lsteins had a higher percentage of u p ­

take than the B r o w n Swiss in the winter and
to the same level in the summer and fall .
(1955) hav e

spring but dropped
Blinc oe and Brody

shown that changing the ambient temperature has a

gre at er effect on some breeds than on others, and this could
be the cause of this apparent Interaction observed in this
study.
The ad d i t i o n of supplemental Iodine, at the level used in
this study, has no apparent effect on the uptake of 1 ^ 1
the thyroid gland of calves.

However,

by

the amount administered

was pr obab ly not In excess of the a n i m a l s ’ needs and further
study should be conducted

to determine the effect of an excess

a m o u n t of iodine on the uptake.
N e i t h e r did Intravenous injections have an effect on the
uptake of l!3l by the thyroid gland.
tained

Hourly counts were o b ­

from the calves re cei vi ng the intravenous Injections

for a period of eight hours to show the rate of uptake of the
isotope.
hours is

The

percent of 24 hour count for the first eight

shown in Table XII for 20 calves.

of the 24- or 48-hour count is plotted,

When the percent

the accumulation of

ll3l over a period of 48 hours is curvilinear but may approach
l i n ea rity over a small

segment of time,

first few hours after injection.

Wh e n

particularly in the
plotted in this manner,

TABLE XII
T H E PERC ENT OF 2 4 -HOUR COUNT AS A MEASU RE OF
RA T E OF UPT A K E FOR THE FIRST FEW HOURS
A F T E R INJECTION OF I 131
Ho ur

Overall
Average

Eight
Holstein

Seven
Br. Swiss

(Ave.)

(Ave.)

Four
Jersey

One
Guernsey

(Ave.)

1

8.6

11.0

5.6

8.3

12 .1

2

14.3

16.7

10.5

15.1

18.4

3

19-7

22 .0

15.7

19.8

28.2

5

29.9

33.1

25.1

29.4

39.4

6

33.7

36.8

2 9 .I

35.0

43.0

7

37.5

41.9

30.0

40.0

44.3

8

43.4

46.5

38.4

44.3

50.3

24

100.0

100.0

100.0

100.0

100.0

there

seems to be no differe nce In the rate of uptake by the

calves of diffe rent breeds as was found in the percent of
I 1^ 1

uptake at 48-hours.

The thyroid gland of the Brown Swiss

calves col lected about the same percentage of the 48-hour uptake
at each

period of time as did the calves of other breeds.

Sinc e the thyroid gland of some animals has the ability
to store iodine,

the percent of I 131 uptake is not a good

me asu re of thyroid output In these animals.

It has been well

demons t r a t e d that In several other species the winter and
spring months are the months

of high thyroid

secretion,

the summer months are a period of low secretion.
before,

whereas

As mentioned

the Iodine content of the thyroid gland of mammals

is hi gh in the summer and low in the spring,
good m e as ure

of output.

The

so It is not a

percent of I 1^1 uptake found in

this

stud y would also suggest that during the summer,

actu al

when the

secret io n Is low, a large amount of iodine is collected

by the gland and

stored

for future need by the body.

The output rate of 1^-31 would be a much better measure of
thyroid
iodine

output,

since It a c tu al ly measures the rate at which

leaves the gland.

As has been

pointed out earlier,

the

a p p a r e n t output rate of da iry calves is very slow, which is
probab ly due to re circ ul at io n of metabolized hormonal iodine,
so could not be used as an indication of activity.

Because

the use of thiouracil was n ec es sa ry to obtain the secretion
rates of the calves,

there may be some influence on the o u t ­

put fr om the gland.

Thiouracil def in ite ly increases the cut-

put as was de monstrate d here and in studies by other workers.
The re su lt s on 22 untreated and 50 treated calves are shown
in Table XIII.
Is not knowna.

Whe t h e r this is the true output rate or not
However,

as long as there Is enough stored h o r ­

mone in the thyroid gland to meet the needs of the animal,
should be no Increase above the normal

output of the hormone.

If there were not enough hormone stored in the gland,
would

then be an increased

from the an t e r i o r

there

production of thyrotropic hormone

pituitary which would cause an increase in

thyroid a c t i v i t y and
the thyroid gland.

there

eventually

an increase in the size of

There were no histological

studies made on

an y of the thyroid glands from the calves used in these trials.
In order to know the effect,

if any,

the thi ou rac il as used In this
need

to be made.

increase d

on the thyroid gland by

technique,

It would appear,

histological

though,

output of thyrotropic hormone,

studies

that if there is an

there should also be

TABLE XIII
E F F E C T OF T H I O UR ACIL OF I131 OUTPUT
OF THE THYROI D GLAND
No .
of
An i m a l s

Gr o u p

Dally
Output
Rate

Treated

50

Standard
Deviation

(days)

w
Un tr eat ed

Biol.
Halflife

Standard
Deviation

3.1

1.5

13.8

7.7

31.3

20.3

6 .6

3 .5

a f u r t h e r b reak in the output curve demonstrated by an increased
output of 1^31 as the thyrotropic hormone Is increased.
effect was not observed in this study.
(1955)

reported

Reineke and Singh

that rats, given thiouracil to prevent further

thyroidal combinat ion of 1^31 during treatment, yielded
roxine

thy­

sec retion rate values ten percent higher than those

not r e c e i v i n g thiouracil.
in this

This

No such comparison could be made

study since it was impossible

to obtain secretion rates

on the calves without thiouracil as demonstrated in Trial 5.
To the a u t h o r ’s knowledge,
vious report of the thyroid
This report,

there has been only one pre­

secretion rate of dairy animals.

made b y Monroe and Turner

calf w e i ghing 72.6 kg.
or 2.06 jug per 100 G.

(19^8),

secreted 1,500 M g D,L-thyroxine
of body weight.

of bo d y weight of L-thyroxine.
method of D e m p s e y and As tw oo d
weight of two thiouracil

per day

This amount is ecjui-

val en t to a loO pound calf secreting 0.^7 mg.

L000 M S a n 8 the other,

stated that a

per 100 pounds

The value was obtained by the
(19^3)

in which the thyroid

treated calves

1,500 jug of

D,

(one calf received

L-thyroxine daily)

were

c o m pa red wit h the av er ag e thyroid weight of three normal calves.

Th ey con c l u d e d

from this com pa ris on that the daily thyroid

s e c r et io n rate was that given above.
in volv ed

in their

study was

Since the number of calves

small and the time of year when

the value was obtained was not stated,
comparison.
va lues

However,

their value does fall in the range of the

obtaine d in this study.

42 cal ves in this

it is hard to make a

The average secretion rate of

study was 0.57 mg.

per 100 pounds of body

wei ght wi t h a standard devia tion of 0.105 mg.

The secretion

rat e of ea c h individual calf can be found in the tables of
each t r i a l .

The av er age secretion rate by breed can be found

in Table XIV.

There is very little difference in the averages

of the breeds.

The B r o w n Swiss calves have the lowest average

se cretion rate, as might be expected because of the temperment
of this breed.

There is much more variation between individuals

w i t h i n a breed than betwe en breeds.
A large seasonal difference in secretion rate found In
other an im al s was not demonstrated in this study due to the
fact that the calves were kept in the barn at all times from
b i r t h until af t e r each trial and were not subjected to extreme
en vir on me ntal changes.

There was a slight difference in the

secretion rate values in studies made in May,
in A u g u s t of the same year.
III) wi th those in A ugust
lower.

These findings

In comparing the May values

(Table IV),

(Table

the latter were generally

support the usual assumption that th y ­

roid a c t i v i t y is dep re ss ed du ring hot weather.
however,

1955* and those

The next year,

trials conducted dur ing the same months did not show

this diffe re nce ,

as can be seen in comparing the values of

Table VIII wi th those of Table IX.

This difference between

TABLE XIV
E S T I M A T E D T H Y R O XI NE SECRETION RATE
OF CALVES B Y BR E E D
Num ber
of
A n ima ls

Breed

Est.
Thyroid
Sec . Rate

Standard
Deviation

(mg./lOO lbs.)

16

0.54

0.4

Guernsey

4

0.63

0.1

Holstein

9

0.60

0.08

13

0.56

0.076

42

0.57

0.105

B r o w n Swiss

Jersey
Overall

the two years can po ssi bly be explained by the fact that the
summer of 1955 was unusually hot and
un usua ll y cool.

the summer of 1956 was

It would have been interesting to have had

the av e r a g e ba rn temperature during the period of time when
each trial was conducted
th rougho ut the year.
en viro nm en ta l

to see h o w much variation there was

It is the author's feeling that the

temperature,

except during the summer of 1955,

was se l d o m outside the range of the comfort zone of cattle.
If this were true,

then the secretion rate values obtained

would not be expected to show any great seasonal variations
but only those di ffer e n c e s due to individual calves.
B e c a u s e ve ry few of the heifers used In this study are now
In production,

it is too early to determine if there is any

co r r e l a t i o n b e t w e e n the uptake of iodine or the thyroid secre­
tion ra te as a calf and the hei fer 's actual
Is as s u m e d

that

production.

It

such a c orre la ti on does exist and a study to

determine
Also,

the deg re e to which it exists would be interesting.

a study to obtain secretion rates on the same animals

whil e they are in production to determine the difference due
to ag e and l a c t at io n might

prove worthwhile.

SUMMARY
A t h y roxi ne
da ily thyroid
scribed.

substit uti on technique for m e a suri ng the

sec retion rate of Intact dairy calves Is d e ­

This met ho d consists of in jecting each calf wit h a

tracer dose of 1 ^ 3 1 t either s u b c ut an eo us ly or intravenously.
F o r t y - e i g h t ho urs later,

a count Is obtained from the thyroid

region of the n e c k and the uptake of the Isotope is determined.
On the sixth d a y a f t e r the In ject ion of the Isotope,
ment of 0.2 g. of thi oura cil

oral t r e a t ­

per kg. of bod y weight is started.

Half of the d a i l y dos age of thiouracil,

ad m i n i s t e r e d b y capsule,

is gi ven In the m o r n i n g and the r e m a i n d e r give n a p p r o x i m a t e l y
twelve hours
ment,

later.

in je ctions

A f t e r four days of the thiouracil

of thy roxine are started.

In this study,

d a i l y in je ctions of L - t h y r ox in e were given

In graded doses of 0.1 mg.

The level was increa se d every second

day, and a thyroid count was obtained

on each dos ag e level

just prior to the I n j e ct io n of the incr eas ed dose.
thyroid

treat­

The d ail y

secretion rate was estim ate d by plo tti ng the corre cted

thyroid count,

computed as

the level of L-t hyro xi ne .

percent of the
The

previous count,

against

point at wh ich the line crossed

100 percent was taken as the thyroid

secretion ra te of that

animal.
The 48 -hour uptake of inject ed

l!3l a v e ra ge d

of the a d m i n i s t e r e d dose for 83 calves.

36.4 percent

A l t h o u g h the uptake

varied b e t w e e n indivi dua ls and trials, B r o w n Swiss h e i f e r s had
a c o m p a r a t i v e l y lower uptake

than the other breeds.

59

The a d d i t i o n

60
of iodized salt to the ration had no apparent effect on the
percent of

collected b y the thyroid gland.

Injecting the

Isotope intravenously made no difference in the 48-hour uptake.
The calves showed the highest average uptake in the summer and
the lowest In the spring.

Younger calves had a higher average

uptake than did the older calves.
The experimental animals demonstrated a very slow output
rate which was assumed to be due to a recycling of metabolized
hormone Iodine.

The output rate could not be Increased by sub­

cutaneous administration of potassium iodide during the exper­
imental period or by including iodized salt at the recommended
level for dairy cattle, but was increased when thiouracil,
at the rate of 0.2 g. per kg. of body weight, was given orally
each day.
The average daily thyroxine secretion rate of 42 calves
was 0.57 nig. per 100 pounds of body weight with a range of

0.36 to 0.84 mg.

LITERATURE CITED
Albert, A. and A. Tenney.
Effect of Iodide, thiouracil and
t hy roxine on the disa pp ea ra nce of thyroidal jt31
proc
Soc. Exptl. Biol. Med.
77:202.
1951.
Ar c h i b a l d , J. G.
Some effects of thyroprotein on the c o m p o ­
sition of milk.
J. Dairy S c i . 28:94l.
1945.
Ast woo d, E. B.
The chemical nature of compounds which Inhibit
the functi on of the thyroid gland.
J. pharm. and Exptl.
Therap.
78:791943Astwo od, E. B. and A. Bissell . Effect of thiouracil on the
io di ne content of the thyroid gland.
Endocrinology
x
34:282.
1944.
Astwood, E. B., J. Sullivan, A. Bissell and R. Tyslowitz.
A c t i o n of certain sulfonamides and thiourea upon the fun c­
tion of the thyroid gland of the rat.
Endocrinology
32:210.
1943.
Ba uma n, E.
tleber das normale Vorko mme n von Jod im Thierkorper.
Z. physiol. Chem. 21:319*
1 8 9 6 . Cited by Kendall and
Simonsen.
J. Biol. Chem.
80:357*
1928.
Bl ax te r, K. L *, E. P. Relneke, E. W. Crampton and W. E. Pe ter ­
sen.
The role of thyroidal materials and of synthetic
go itro g e n s in animal production and an appraisal of their
practical use.
J. Animal Sci.
8:307*
19^9*
Bl inco e, C.
In vivo determin ation of thyroid l!3l of dairy
cows.
NucTeo nic s 11:70*
1953*
Bl inco e, C. and S. Brody.
The influence of ambient te mpe ra­
ture, air velocity, radiation intensity, and starvation
on thyroid act i v i t y and Iodine met abolism in cattle.
Mo. Agr. Expt. Sta., Res e a r c h B u l l . 576.
1955a.
and
. The influence of diurnally variable
te mp er atur es on the thyroid activity and iodide metabolism
Qp jersey and Ho ls te in cows.
Mo. Agr. Expt. Sta., Research
Bull. 579*
1955b.
Brody, S. and R. F. Frankenbach.
Age changes in size, energy
m e t a b o l i s m and cardiore sp ir at ory activities of thyroidecto
mi z e d cattle.
Mo. Agr. Expt. Sta., Research Bull.
3 9*
19^2.

6l

62
Chanda, R., m. L- M c N a u g h t and E. C. Owen.
The effect of thio­
uracil and th yro xine on the compositio n of milk.
(abs )
Brit. J. N u t r i t i o n
6 :x.
1952 a.
------- 3— j * ___________a n d _____________ . The effect of thvroxine
and thi or uacll on the compositi on of milk.
3 . The co n c e n ­
tr at io n of the ma jor constituents and of some of the water
soluble vit amins in cow's milk.
Biochem. J.
51:543.
1952b
Clarke, E. L. and E. M. Boyd.
A seasonal study of the iodine
content of the blood of birds.
J. Biol. Chem.
135:691.
1 940

.

Cruickshank, E. M.
Observation s on the iodine content of the
thyroid and ovary of the fowl during the growth, laying
and m o u l t i n g periods.
Biochem. J.
23:1044.
1929 .
Curtis, G. M ., C. B. Davis and F. J. Phillips.
Significance
of the iodine content of human blood.
J. Am. Med. Assoc.
1 0 1 :9 0 1 . 1 9 3 3 .
Dempsey, E. W. and E. B. Astwood.
Determination of the rate
of thyroid hormone secretion at various environmental
tempera tur es.
E n d o cr in ol ogy
32:509*
1943.
Ely, R. E., K. J. Olson and E. P. R e i n e k e . Absorption and
el im i n a t i o n of thioruacll in ruminants.
J. Animal Sci.
7 :2 0 8 . 19^8.
Foster, G. L. and P. E. Smith.
Hypophysec tom y and replacement
t h e r a p y in relation to basal met abo lism and specific
dyna mic a ctio n in the rat.
J. Am. Med. Assoc.
87:2151.

1926 .
Franklin, A. L. and I. L. Chaikoff.
The effect of sulfonamides
on the con version in vitro of inorganic iodide to thyroxine
an d d l i o d o t y r o s i n e T y thyroid tissue with radioactive iodine
as indicator.
J. Biol. Chem.
152:295*
1944.
Franklin, A. L., I. L. Chaikoff and S. R. L e r n e r . The influence
of go itrogenic substances on the conversion in vitro of
in org anic iodide to thyroxine and diiodotyrosTne by th y ­
roid tissue wi th rad io active iodine as indicator.
J.
Biol . Chem.
153:151*
1944.
Franklin, A. L*> S. R* Lerner and I. L. Chaikoff.
The effect
of thiouracil on the formation of thyroxine and diiodotyrosine b y the thyroid gland of the rat with radioactive
i o din e as indicator.
Endo cr ino logy
34:265*
1944.
Fredrick son , D. S., W. F. Ganong and D. M. Hume.
Thyroid u p ­
take of r a di oa ct ive iodine in the dog; effect of die ,
hypophys ec to my , and T S H . Proc. S o c . Exptl. Biol. Med.
89:4l6.
1955*

63

Go ld smi th , R. E., J. B. St anbu ry and G. L. Brownell.
The
ef fe ct of t h yr ot ro pi n of the rel ease of hormo ne from the
h u m a n thyroid.
J. Cl in ica l E n d o c r i n o l o g y
11:1079.
1951.
Graham, W. R., Jr.
The ef fect of t h y roi de ct om y and thyroid
f e e d i n g on the m i l k secretion and mi lk fat production of
cows.
J. N u t r i t i o n
7:407.
1934a.
The ac t i o n of thyroxine on the milk and milk-fat
p ro du ction of cows.
Biochem. J.
28:1368.
1934b.
Hamilton, J. G.
The rates of a b s o rp ti on of the radioactive
isoto pe s of sodium, potassium, chlorine, bromine and iodine
in normal h u m a n subjects.
Am. J. Physiol.
124:667.
1938.
Hamilton, J. G. and M. H. Soley.
Studies in iodine metabolism
b y the use of a n e w radioa cti ve isotope of iodine.
Am.
J. Physiol.
1 2 7 :5 5 7 . 1939and
. Studies in iodine metabolism of the
thyroid gland- in” situ by the use of radio iodine in normal
subjects and in patients with various types of goiter.
Am. J. Physiol.
131:135.
19^0.
Harington, C. R. Ch em istr y of thyroxine
I. Isolation of th y­
ro x i n e fro m the thyroid gland.
Biochem. J.
20:293.
1926.
Harington, C. R. and G. Barger,
Chemi str y of thyroxine.
III. Con s t i t u t i o n and synthesis of thyroxine.
Biochem. J.
21:169.
1927.
Hen neman, H. A., S. A. Griffin and E. P. Reineke.
A deter­
m i n a t i o n of thyroid secretion rate in intact individual
sheep.
(abs.) J. Animal Sci.
11:794.
1952.
Henneman, H. A., E. P. Reineke and S. A. Griffin.
The thyroid
se cretion rate of sheep as affected b y season, age, breed,
pregnancy, and lactation.
J. Animal Sci.
14:419.
1955Herman, H. A., W. R. Graham, Jr. and C. W. Turner.
The effect
of thyroid and thyroxine on mi lk secretion in dairy cattle.
Mo. Agr. Expt. Sta., Re searc h Bull.
2 7 5 . 1938.
Hertz, S. and A. Roberts.
Radioactive iodine as an indicator
in thyroid physiology.
III. Iodine collection as a c r i ­
terion of thyroid function in rabbits injected with th y­
ro tr op ic hormone.
En do cr ino logy
2 9 :8 2 . 1941.
Hertz, S., A. R ob erts and R. D. Evans.
Radioactive iodine as
an i n d i c a t o r in the study of thyroid physiology.
Proc.
Soc. Exptl. Biol. Med.
38:510.
1938Hertz, S., A. Roberts, J. H. Means
and R. D. Evans.
Radio­
a c t i v e iodine as an In dicator in thyroid physiology.
Iodine col le ct io n by normal and hyperplastic thyroids
rabbits.
Am. J. Physiol.
128:56519^0.

64

H Ig hle y, D. R ., H. E. Parker and F. N. Andrews.
Qua nt it at ive
I n t e r r e l a t i o n s h i p s b e tw ee n the effects of iodine and t h i o ­
uracil on thyroid function.
J. Nu t r i t i o n
54:249.
1954.
Jack, E . L . and S . I. Bechdel.
rox in e on mi lk s e c r e t i o n .

A study of the influence of thyJ. D a i r y Sci.
15:195.
1935.

Joliot, F. and I. Curie.
A rt if icia l production of a new kind
of r adio -e le me nt.
Natur e (London)
133:201.
1934.
Keating, F. R .,Jr., R . W. Rawson, W. Peacock and R. D. Evans. The
c o l l e c t i o n and loss of r a di oa ct ive iodine compared with a n a ­
tomic changes induced in the thyroid of the chick b y the in-'
jection of thyr otropic hormone.
End oc ri no logy
36:137.
1945
Ke mme rer, A. R., R. A. Bolomey, M. G. Vav ic h and R. N. Davis.
E f f e c t of th yr op ro te in on the vitamin content of milk.
Proc. S o c . Exptl. Biol. Med.
63:309.
1946.
Ke nda ll,
E. C.
The de te rmin at io n of
studies In thyroid activity.
J.

Iodine in connection with
Biol. Chem.
19:251. 1914.

Kendall, E. C. and D. G. Simonsen.
Seasonal variations in iodine
and thyro xine content of the thyroid gland.
J. Biol. Chem.
80:357.
1928.
Kennedy, T. H. and H. D. Purves.
Studies on experimental goitre.
I. The effect of Brass ic a seed diets on rats.
Brit. J.
Exptl. Pat ho lo gy
22:241.
1941.
Leblond,
C. P., J. Gross, W. Peacock and R. D. Evans.
Metabo­
lism
of radio -i od in e in the thyroids of rats exposed to high
or low temperatures.
A m J. Physiol.
140:671.
1944.
Lewis, R. C.
Protein-bound iodine levels In dairy cattle plasma,
milk, and colostrum.
Ph.D. thesis. Michigan State College.
1952.
Livingood, J. J. and G. T. Seaborg.
Radioactive isotopes of
iodine.
Physical Re v i e w
54:775*
1938.
Long, J. G., L. 0. Gilmore, G. M. Curtis and D. C. Rife.
The
bo vi ne protein-bound iodine as related to age, sex, and
breed.
(abs.)
J. Animal Sci.
10-.1027.
1951.
MacKen zie , C. G. and J. B. MacKenzie.
Effect of sulfonamides
and thi oureas on the thyroid gland and basal metabolism.
Endocrinology
32:185.
1943.
M ac Ke nz ie, J. B., C. G. MacKenzie and E. V. McCollum,
of sulf ani lv lg uanid in e on the thyroid of the rat.
94:518,
19^1.

The effect
Science

M a g n u s —levy, A*
Uber den resplr at ori schen Gaswechsel unter ^em
Fl nf la ss der Thyroidea sowie unter verschiedenen pathologische
Z u s t a n d e n . Berl . Klin. Wchnschr.
32:650.
1^95.
Cited from
r
D
Turner.
General E n d o c r i n o l o g y . W. E. Saunders Company.
Philadel ph ia and London.
1948.

65
M a r i n e j, D.
Q u a n t i t a t i v e studies on the in vivo a bs o r p t i o n of
i o din e by dogs' thyroid glands.
J. B T o l C h e m .
22:547.
1915.
_______
• The pathogenesis and prevention of -simple or
endemic goiter.
J. Am. Med. Assoc.
104:2334.
1935.
Milien, T. W., W. B. Nevens and K. E. Gardner.
The effects of
f e e d i n g t h y r o p r o t e i n (protamone) to da iry calves.
(abs.)
J. A n im al Sci.
7:543.
1948.
Mixner, J. P., E . P. R e i n e k e and C. W. Turner.
Effect of t h i o ­
uracil and thiourea on the thyroid gland of the chick.
Endocrinology
34:168.
1944.
Monroe, R. A. and C. W. Turner.
Thyroid secretion rate of
a l b i n o rats d ur in g growth, pregnancy and lactation.
Mo.
Agr. Expt. Sta., Re s e a r c h B u l l . 403.
1948.
Morton, M. E. and I. L. Chaikoff.
The formation in vitro of
t hy roxine and dii o do ty ro sine by thyroid tissue-'with "radioa c t i v e iodine as an indicator.
J. Biol. Chem.
147:1.
1943.
Morton, M. E., I. L. Chaikoff, W. 0. Rei nhardt and E. Anderson.
R a d i o a c t i v e iodine as a n indicator of the met abo li sm of
iodine.
VI. The formation of thyroxine and diiodotyrosine
by the c ompl et el y thyroidectomi zed animal.
J. Biol. Chem.
147:757.
1943.
Morton, M. E., I. L. Ch aik off and S.Rosenfeld. Inhibiting
effect of inorganic Iodide on the formation in vitro of
t hy roxine and di io dot yro sine by surviving thyroid t i s s u e .
J. Biol. Chem.
154:381.
1944.
Morton, M. E., I. Perlman, E. An d er so n and I. L. Chaikoff.
R a d i o a c t i v e Iodine as an Indicator of the met ab oli sm of
iodine.
V. The effects of hy po phy sec tomy of the d i s t r i b u ­
tion of labelled thyroxine and diiodotyrosine in thyroid
gland and plasma.
End oc rinol og y
30:495.
1942.
Morton, M. E., I.Perlman and I. L. Chaikoff. Radioactive
iodine as an ind icator of the met abo lism of iodine.
III. The effect of thyrotropic hormone on the turnover of
thyroxine and diiodoty ro si ne in the thyroid gland and
plasma.
J. Biol. Chem.
l40:603.
1941.
M u l i n o s , M. G. and L. Pomerantz.
Ps eu d o - h y p o p h y s e c t o m y . A
co n di ti on res embl in g hypophysectomy produced by m a l n u t r i ­
tion.
J. Nutr it io n
19:493.
1940.
Perlman, I.* I* I* * Chaikof f and M. E. Morton.
Radioactive
iod in e as an indicato r of the
met abolism of iodine. I.
The t ur no ve r of Iodine In the
tissues of the normal animal,
wi th particular reference to the thyroid.
J. Biol. Chem.
139:^33.
1941.

66

Perlman, I., m . E. Morton and I. L. Chaikoff.
Rad i o a c t i v e
i odin e as an in d i c a t o r of the m e t a b o l i s m of iodine.
II.
The rates of formatio n of th yroxi ne and di io dot y r o s i n e
by the intact normal thyroid gland.
J. Biol. Chem.
139:449.
1941.
>
and
. R a d i o a c t i v e iodine as
an I n d i c a t o r of t h e m e t a b o l i s m of iodine.
IV. The d i s t r i ­
b u t i o n of labelled thyroxine and d i i o do ty ro sine in liver,
mu s c l e and small intestine.
Endocrinology
30:487.
1942.
Perry, W. F.
A method for m e a s u r i n g thyroid horm one secretion
in the rat with its a p p l i c a t i o n to the bio as sa y of thyroid
extracts.
Endocrinology
48:643.
1931.
Petersen, W. E., A* Spielman, B- S. Pomeroy and W. L. Boyd.
Ef fe ct of th yr o i d e c t o m y upon sexual behavior of the male
bovine.
P r o c . Soc. E x p t l . Biol. Med.
46:l6.
1941.
Pipes, G. W., B. N. Premach andr a and C. W. Turner.
A technique
for in vivo m ea su re ment of thyroid il3l qn cattle and its
a p p l T c a T T o n dur ing experimental al te rat ion of thyroid
function.
J. Animal Sci.
(abs.) 15:1292.
1956.
Pipes, G. W. and H. R u p p e r t . Estimati on of the L-thyroxine
secretion rate of dairy animals.
(abs.) J. Ba iry Sci.
3 8 : 5 l 0 . 1955 *
Pipes, G. W. and C. W. Turner.
The effect of thryoxine on
thyroid function as shown by 1^31.
Conference on R a d i o ­
a c tiv e Isotopes in Agriculture.
Michigan State University,
East Lansing,
Michigan.
1956,
Puntriano, G. and J, Meites.
The effects of
or darkness on thyroid function in mice.
48:217*
1951.

continuous light
Endocrin olog y

Quimby, E. H., S. C. W e rn er and C. Schmidt.
Influence of age,
sex, and season upon radioiodine uptake by the human thyroid
Proc. Soc. Exptl. Biol. Med.
75:5371950.
Ralston, N. P., W. C. Cowsert, A. C. Ragsdale, H. A. Herman
and C. W. Turner.
The yield and composition of the milk
of d airy cows and goats as influenced by thyroxine. Mo.
A g r . E x p t . Sta., Re s e a r c h Bull.
317*
1940.
Ra n d a l l
R. V. and A. Albert.
The effect of hypophys ect omy
on the uptake of radioactive Iodine by the thyroid of the
rat.
E n d o c r inol og y
48:3271951.
Rapport, R. A. and G. M. Curtis.
The clinical significance
of the blood iodine: A review.
J. Clinical Endocrinology
10:7351950.

Reece, R. p. and E. B. Man.
S e r u m precipitable and butanol
e x t r a c t a b l e Iodine of b ov in e sera.
P r o c . Soc. Exptl.
Biol. Med.
79:208.
1952.
R e f o r z o - M e m b r i v e s , J.
T h y r o i d - I n h i b i t i n g a c ti on of the h y p o ­
physes of rats fed wit h thyroid.
En do cr i n o l o g y
32:263.

1943.
R e i n e k e , E. P.
The effect of thy rol actin on milk production,
m e t a b o l i s m and growth.
(abs.) J. D a i r y Sci.
25:701.
1942.
_______________ Practical trials on the use of synthetic thyroprotein for increased production of milk and butterfat.
(abs.) J. D a i r y Sci.
26:750.
1943.
- The effect of synthetic thyroprotein on sterility
in b u l l s . The problem of fertility.
Princeton Univers ity
Press, Princeton, N. J.
1946.
Reineke, E. P., J. P. Mix n e r and G. W. Turner.
Effect of graded
doses of thyroxine on m e t a b o l i s m and thyroid weight of rats
treated with thiouracil.
E n d o crinol og y
36:64.
1945.
Reineke, E. P. and 0. N. Singh.
Estimati on of thyroid hormone
secretion rate of intact rat.
Proc. Soc. Exptl. Biol. Med.
88:203.
1955.
Reineke, E. P. and 0. W. Turner.
Growth response of thyroidectomized goats to a r t if ic ia lly formed thyroprotein.
Endocrinology
2 9 :6 6 7 . 1941.
ho rm on e
1945.

and
. Seasonal rhythm in the thyroid
secretion of~the chick.
Poultry Sci.
24:499.

Richter, G. P. and K. H. Clisby.
Graying of hair produced by
in gest io n of p h e n y l t h i o c a r b a m i d e . Proc. Soc. Exptl. Biol.
Med.
48:684.
1941.
Salmon, T. N. and A. E. S e v r i n g h a u s . Functional auto- and
homo-plas ti c thyroid grafts in the rat.
Proc. Soc. Exptl.
Biol. Med.
34:251.
1936.
Salter, V/. T., A. M. Ba ss et t and T. S. Sappington.
Proteinbound iodine in the blood.
VI. Its relation to thyroid
fu nction in 100 clinical cases.
Am. J. Med. Sci.
202:527.
1941 .
S c h a c h n e r , H., A. L. F r a n k l m and I • L « C h a i k o f f . On the i n
vitr o acc u m u l a t i o n of inorganic Iodide by surviving thyroid
tl’s"s"ue with r adi oactive Iodine as an indicator.
Endocrin­
ol ogy
34:1591944.

68

Schultze, A. B. and C. W. Turner.
The det erm ination of the
rate of thyroxin e secretion by certain domestic animals.
Mo. Agr. Expt. Sta., R e s e a r c h B u l l . 392.
1945.
Seiden, A. and P. Penger.
Seasonal var iation in the iodine
co nte nt of the thyroid gland.
J. Biol. Chem.
13:517.
1913.
Singh, 0. N., H. A. H e n ne ma n and E. P. Reineke.
The r e l a t i o n ­
ship of thyroid a c t i v i t y to lactation, growth, and sex in
sheep.
(abs.)
J. Animal Sci.
13:1031.
1954.
Spielman, A. A., W. E. Petersen, J. B. Fitch and B. S. Pomeroy.
General appearance, grow th and rep roduction of thyroidectomized bovine.
J. D a i r y Sci.
28:329.
1945.
Thomas, J. W. and L. A. Moore.
Thyroprotein feeding to dairy
cows dur ing successive lactations.
J. Dairy Sci.
3 6 :6 5 7 .
1953*
Turner, C. W.
Effect of age and season on the thyroxine secre­
tion rate of Wh ite Leghorn hens.
Poultry Sci.
27:146.
1948.
Turner, K. B., A. De La mater and W. D. Province.
Observations
on the blood iodine.
I. The blood iodine in health, in
thyroid and cardiorenal disease, and in leukemia.
J. Clin.
Invest.
19:5151940.
Va nLan di ng ha m, A. H., H. 0. Hen derson and C. E. Weakley.
The
ef fect of iodlnated casein (protamone) on milk and butterfat production and on the ascorbic acid content of the
milk.
J. D a i r y Sci.
2 7 :3 8 5 . 1944.
Van Lan di ng ham, A. H., G. Hyatt, C. A. Weakley, Jr. and H. 0.
He nderson.
Fur the r observations on the effects of feeding
th yro pro te in to dairy cows.
(abs.) J. Dairy Sci.
30:576.
1947.
Werner, S. C., H. B. Hamilton, E. Leifer and L. D. Goodwin.
A n appra isa l of the radioiodine tracer technic as a clinical
procedure in the diagnosis of thyroid disorders.
J.
Cli nic al En do c r i n o l o g y
10:1054.
1950.
Werner, S. C., E. H. Quimby and C. Schmidt.
The use of tracer
d os es of ra dioactive iodine, I 1^1 , In the study of normal
and disorder ed thyroid function In man.
J . Clinical
Endocrinology
9:342.
1949*
Wolff, J.
Some factors that influence the release of iodine
fr om the thyroid gland.
Endocrin olo gy
48:u84.
1951.