The regulation of androgen and estrogen formation in fetal gonads

Several aspects of the functional development of the testis and ovary have been characterized in the fetal rabbit. First, the capacity of the fetal ovary to form 17β-estradiol develops at the same time in embryogenesis as the onset of testosterone formation in the fetal testis. Second, both fetal ovaries and testes have the capacity to form these steroid hormones from cholesterol de novo. Third, the enzymatic differentiation of the fetal testis occurs at the expected time in organ culture suggesting that this aspect of development is not hormone-induced. Fourth, gonadotropin receptors appear in testes concomitant with the initial rise in testosterone content but are virtually absent in ovaries throughout gestation. However, the onset of testosterone synthesis and the initial rise in testosterone content in the fetal testis do not appear to be coupled to gonadotropin stimulation since hCG does not stimulate testosterone formation until late in embryogenesis.