In vitro steroid metabolic studies in human testes I: Effects of estrogen on progesterone metabolism.

ABSTRACT

PIP: 4 male transsexuals, aged 23-46 years, were treated with ethinyl estradiol (1-2 mg daily) for at least 12 months prior to orchiectomy and sex-change surgery. The pattern of in vitro steroid biosynthesis by testicular tissue before and after this therapy was examined histologically and hormonally. Serum follicle stimulating hormone and luteinizing hormone were measured by radioimmunoassay as were plasma and testicular concentrations of testosterone (T). Plasma estradiol (E) and testicular progesterone (P) were also measured. In vitro steroid biosynthetic studies were made with radiolabeled precursors. Histology showed a uniform picture of spermatogenic arrest at the primary spermatocyte level after treatment. Concentrations of T, P, E, and 20alpha-dihydroxyprogesterone in the testes of the treated men showed that all hormones except E decreased markedly. Biosynthesis studies demonstrate that radioactive P substrate was poorly metabolized. In vitro synthesis of T from P was severely impaired; 17alpha-hydroxylation decreased substantially while 20alpha-hydroxy-steroid-dehydrogenase activity increased after estrogen treatment. It is suggested that 17alpha-hydroxylase activity is either under gonadotropin regulation or is directly inhibited by estrogen treatment. The increase in 20alpha-reduction might represent an alternate pathway unaffected by the treatment.