Hypothalamic and Pituitary Regulation of Adrenocortical Function in the Hamster: Effects of Gonadectomy and Gonadal Hormone Replacement1

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Abstract
Prepuberal gonadectomy in the hamster resulted in greater pituitary content of ACTH in adult castrates than in intact controls. Testosterone or estradiol replacement did not restore pituitary ACTH content to intact levels. Daily administration of ACTH for 2 weeks resulted in adrenal enlargement in all groups, abolished or reversed the diminutions in adrenal weight, plasma steroids, and adrenal slice steroid output observed after orchiectomy, and abolished the diminution in adrenal weight observed after ovariectomy. Pituitary content of ACTH was markedly diminished after ACTH injections in intact males and females in comparison with saline-injected controls. Pituitary release of ACTH in vitro was similarly reduced in ACTHtreated males. Testosterone replacement stimulated adrenal weight and hepatic metabolism of the side-chain of cortisol in vitro in hypophysectomized, castrated males but failed to alter adrenal slice steroid output or hepatic metabolism of ring A. Estradiol had no effect on adrenal weight, adrenal slice steroid output, or hepatic metabolism of cortisol in vitro in hypophysectomized, castrated females. Minor alterations of pituitary release of ACTH in vitro and hypothalamic content of corticotropin-releasing activity were observed after gonadectomy or gonadal hormone replacement. The data indicate that the gonads influence the hypothalamic-pituitary-adrenal axis of the hamster at multiple sites. In the male, the observations are consistent with the hypothesis that testosterone enhances ACTH secretion, leading secondarily to increased adrenal steroid secretion and increased hepatic metabolism of cortisol. Changes in the female are of equivocal physiologic significance. Comparison with previous findings in the rat reveals numerous divergences, indicating different mechanisms of action of the gonads on the hypothalamic-pituitary-adrenal axis in the two closely-related species. (Endocrinology89: 1047, 1971)

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