Age-related changes in endogenous steroids of human fetal testis during early and midpregnancy.

The steroidogenic activity of human fetal testes during early and midgestation was monitored by analyzing 58 individual fetal testes (aged 6-20 weeks of pregnancy) for endogenous pregnenolone (P5), progesterone, 17-hydroxyprogesterone, dehydroepiandrosterone, androstenedione, testosterone (T) and estradiol. A clear increase in testicular steroid concentrations, especially in those of T and other 3-keto-4-ene steroids, occurred between 8-11 weeks of gestation and reached maximum between 11-14 weeks. The three steroids present in highest concentrations were P5, androstenedione, and T (maximum concentrations, 1.9-2.7 ng/mg wet tissue). The levels of all of the C-19 steroids measured decreased clearly between weeks 14-20 of gestation, whereas those of the C-21 steroids, P5, progesterone, and 17-hydroxyprogesterone, remained relatively high. Our results suggest that the metabolic reactions converting P5 to androgens are activated in the human fetal testis within a short time range between 8-11 weeks of gestation. The increased androgen production is possibly a consequence of increased 3 beta-hydroxysteroid dehydrogenase activity. Testicular androgen production decreases in the beginning of the second trimester of pregnancy, most likely due to a blockade in the C-21 steroid side-chain cleavage.