Interaction of Growth Hormone and ACTH in the Regulation of Adrenocortical Secretion in Rats

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Abstract
Effects of growth hormone, alone or in combination with ACTH, on adrenal function in hypophysectomized rats were examined. Hypophysectomy reduced corticosterone secretion and increased adrenal 5α-reductase activity. Growth hormone, administered alone to hypophysectomized rats, lowered reductase activity without affecting corticosterone secretion. ACTH alone increased corticosterone output but only partially reversed the increment in reductase activity. As a result, ACTH-treated rats secreted large amounts of 5α-dihydrocorticosterone (DHB) and 3β-5α-tetrahydrocorticosterone (R), the principal adrenal metabolites of corticosterone. Growth hormone, when given with ACTH, potentiated the effects of ACTH by stimulating corticosterone secretion and lowering 5α-reductase activity further. The additional increment in corticosterone resulted in part from a decline in the secretion of DHB and R. These results indicate that growth hormone plays a role in the maintenance of adrenocortical secretion which is at least partially mediated by effects on adrenal 5α-reductase. (Endocrinology93: 188, 1973)

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