Studies on Human Sexual Development. I. Fetal Gonadal and Adrenal Sex Steroids¹

Testosterone and estradiol concentrations were measured by isotope-displacement assays in the gonads and adrenals of 54 human fetuses (33 male, 21 female) delivered by hysterotomy. Results were correlated with crownrump (CR) length which ranged from 5 to 24 cm, corresponding to 10–25 weeks fetal age. Testosterone concentration averaged 1400 pg/mg in the testes but was negligible (<90 pg/mg) in the ovaries and in the adrenals of both sexes. Testosterone was found in appreciable amounts in the testes from the youngest specimens, reached a peak at 7–10 cm CR-length and declined by 13–14 cm CR-length. Little or no estradiol was detected in fetal testes, ovaries and adrenals and there were no sex differences in these levels. These data provide evidence that human fetal testicular tissue accumulates testosterone in a pattern suggesting higher androgen production at the time of male genital differentiation.