Pituitary Hormones Affecting Adrenal 5α-Reductase Activity: ACTH, Growth Hormone and Prolactin1

Adrenal 5α–reductase activity in cortisone—treated rats is increased 2.5–fold after hypophysectomy. Treatment of hypophysectomized rats with either TSH or FSH plus LH did not affect reductase activity whereas ACTH, prolactin or growth hormone each exerted an inhibitory effect. When ovariectomized rats were treated either with TSH, ACTH, growth hormone or prolactin, only prolactin lowered reductase activity. Ovariectomized rats responded to prolactin at doses as low as 10 μg/lOOg bw. The hormone was also effective in orchiectomized animals. Treatment of ovariectomized rats with prolactin also enhanced the output of corticosterone by adrenal slices in vitro while not affecting the production of total corticosteroids. The data suggest that the stimulation of reductase activity after hypophysectomy results from the withdrawal of prolactin and growth hormone, as well as ACTH. In the gonadectomized rat, however, prolactin is the only effective pituitary hormone. Prolactin apparently stimulates the output of corticosterone by inhibiting the formation of reduced steroid metabolites.(Endocrinology91: 764, 1972)