ADRENOCORTICAL FUNCTION AFTER ADMINISTRATION OF THYROXINE AND TRIIODOTIIYRONINE IN RATS’

Adrenal changes in hyperthyroidismn and thyrotoxicosis and during thyroxine administration have been reported in man and laboratory animals. Whereas the results of studies on adrenocortical function in hyperthyroidism and thyro-toxicosis in man are still equivocal because the abnormalities disclosed have not been very pronounced or consistent, the weight of evidence obtained from animal experiments is in favor of a stimulatory influence of thyroxine on the adrenal cortex, probably secondary to an increased release of adrenocorticotrophic hormone. In view of recent experiments showing that some of the actions of thyroid hormones are mediated through stimulation of the hypophyseal-adrenocortical system (Eartly and Leblond, 1954; Timiras ci al., 1955) and because of the similarity of action between thyroxine and triiodothyronine on various systems and functions, it was considered of primary interest, in the present study, to investigate in the rat the comparative effects of thyroxine and triiodothyronine on adrenocortical function