In vitro steroid metabolic studies in testicular 17 beta-reduction deficiency.

In order to document testicular 17beta-reduction deficiency (17RD) and to search for additional metabolic aberrations possibly associated with this disorder, the metabolism of 14C-labeled pregnenolone (delta5P), 17-HYDROXYPROGESTERONE (17OHP), dehydroepiandrosterone (DHEA), androstenedione (A), testosterone (T) and estrone (E1) was studied in testicular minces from a 46-year-old male pseudohermaphrodite (MPH) with highly elevated testicular A and minimal T secretion but normal extragonadal conversion of A to T. Testicular minces from a 20-year-old MPH with apparently normal testicular T biosynthesis served as a control. The results of this investigation show that the 17RD testes metabolized delta5P along delta5- and delta4- pathways but, in contrast to the control, converted more 17OHP, metabolizing it predominantly to A rather than T, failed to reduce DHEA to androst-5-ene-3beta,17beta-diol, metabolized DHEA very efficiently to A and produced little T, and converted only minimal quantities of A and E1 to their 17beta-reduced counterparts. 17beta-Reduction increased slightly but was far from being restored to control levels upon addition of NADH plus NADPH. However, oxidation of T to A by 17RD testicular minces, with and without additional NAD plus NADP, was comparable to that by the control. These results document 17RD for A, DHEA and E1 and suggest that the lack of elevated 17OHP and DHEA secretion by the 17RD testes was due to increased 17, 20-lyase and perhaps elevated 3beta-hydroxysteroid dehydrogenase and/or isomerase activity. The observation that 17beta-reduction was only slightly increased upon addition of NADH plus NADPH, but that oxidation of T to A was normal, is consistent with the assumption that more than one 17beta-hydroxysteroid dehydrogenase may be involved in testicular 17beta-reduction and/or 17-oxidation, and that the 17RD testes studied either lacked the enzyme which acts predominantly as 17beta-reductase or that the affinity of this 17beta-reductase for reduced cofactor(s) and/or substrates was abnormal.