In vitro conversion of progesterone in the human testis at different ages, pathophysiological conditions, and during treatment with estrogens or gonadotrophic hormones.

The enzyme 17 alpha-hydroxylase catalyzes the conversion of progesterone to 17 alpha-hydroxyprogesterone in the testis and may be studied with the use of incubation of testicular tissue with [3H] progesterone in vitro. The enzyme 20 alpha-hydroxysteroid dehydrogenase catalyzes the conversion of progesterone to 20 alpha-dihydroprogesterone. These enzymes were studied in testicular tissue from 105 human males regarding the effects of aging, different pathophysiological conditions, and gonadotrophic or estrogenic treatment. 17 alpha-Hydroxylase activity was low in vitro in testicular tissue from prepubertal boys, adult men with pituitary tumors, and estrogen-treated elderly men. In nontreated elderly men and certain infertile adult men, 17 alpha-hydroxylase was more active than in the above-mentioned patient groups, albeit lower than in adolescent and adult men. Gonadotropic treatment increased the conversion mediated by 17 alpha-hydroxylase in prepubertal as well as adult testicular tissue. In conclusion, the activity of 17 alpha-hydroxylase may be influenced by gonadotrophic hormones and may be an indicator of the testicular endocrine state at the moment of biopsy. Testicular 20 alpha-hydroxysteroid dehydrogenase seems to be active during low gonadotrophic influence and might even be inhibited by gonadotrophic stimulation.