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Abstract
The immediate and long-term effects of thyroxine administration to neonatal rats have
been studied. As compared with control animals the rats given 216 μg thyroxine during
the first 2 weeks of life showed accelerated maturation as manifested by earlier eye
opening and greater early locomotor activity. The treated animals displayed a diminished
growth rate which persisted for the 20 weeks of observation, and the growth rate was
not altered by replacement thyroxine. Sexual maturity was demonstrated by the experimental
animals at approximately the same age but body weight was significantly lower than
that of control animals. Reproductive performance differed only in that the rats given
thyroxine in infancy had fewer pups per litter. Evidence of a permanent alteration
of thyroid status was provided by a decrease in the relative weight of the thyroid
gland persistent for at least 18 weeks after the last thyroxine injection. Eight weeks
after completion of thyroxine treatment the experimental animals had identical 18
hour thyroidal uptake of 131I, decreased serum protein-bound 131I, and decreased rebound in thyroidal 131I uptake following methimazole treatment, as compared with control animals.
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References
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Article info
Publication history
Accepted:
October 5,
1968
Received:
July 30,
1968
With the technical assistance of MICHAEL M. BESTFootnotes
☆Supported by Research Grant HE-01946 from the National Heart Institute, United States Public Health Service, and Eli Lilly & Company.
Identification
Copyright
© 1969 Published by Elsevier Inc.
