In vitro metabolism of progesterone by the human undescended testis

Testicular biopsy specimens from 28 boys with undescended testis, and from 6 men operated post-pubertally for undescended testis, were incubated in vitro with [3H]progesterone (P). Significant steroid metabolic activity was demonstrated in all biopsies. Before puberty the total conversion rate was low and only a small amount of 17 alpha-hydroxy-progesterone (17 alpha-OH-P) was formed. The amount of newly formed 20 alpha-dihydro-progesterone (20 alpha-DH-P) was relatively constant regardless of increasing maturity. After puberty the total conversion rate was higher. More 17 alpha-OH-P was synthesized, and the ratio between formed 20 alpha-DH-P and 17 alpha-OH-P decreased significantly. The position of the undescended testis did not appear to influence progesterone metabolism. In no case could we demonstrate deficient steroidogenesis. In one 17-year old boy the 20 alpha-DH-P/17 alpha-OH-P ratio was lower in the undescended testis (0.9) than in the scrotal testis (4.0) suggesting increased steroidogenesis per mg tissue in the malpositioned testis. The indication from the present study, that even grossly displaced testes have a relatively undisturbed steroidogenic capability, suggests that the reason for impaired descent may not simply reflect disturbed androgen synthesis, but must involve other mechanisms.