Failure of Adrenalectomy To Alter Either Thyroid Activity During the Estrous Cycle or Thyroidal Response to Exogenous Estrogen in the Rat

Gonadectomized-adrenalectomized male and female rats were given a single injection of 50 μg of estradiol benzoate and T:S ratios were determined at intervals up to 72 hr thereafter. T:S was depressed in females 18 and 24 hr after injection, but there were no consistent alterations in T:S of males during this interval. Iodide concentrating activity was stimulated in both sexes after 36 hr. These results are similar to those previously obtained in the presence of the adrenals and indicate that corticosteroids do not play a significant role in thyroidal response to exogenous estrogen. AdrenalectomizedAdrenalectomized female rats were also studied during various stages of the estrous cycle. Over 30% displayed abnormalities of vaginal cycles ranging from anestrus to persistent estrus, while in those undergoing normal cycles an excessive number of leukocytes appeared in the vaginal smears during metestrus and diestrus. Cyclic variations in T:S ratios of adrenalectomized rats did not deviate significantly from those of intact animals, indicating that adrenal corticoids are likewise not of physiologic importance in thyroidal response to endogenous estrogen. (Endocrinology83: 1366, 1968)