Effects of androgen injections and decapitation on the pituitary-gonadal axis and genital tract of fetal rats at the end of gestation.

The relationships between LH activity in the plasma, testicular and plasma levels of testosterone and prostatic buds were examined on day 21 of gestation in control and experimental male fetal rats. Surgical hypophysectomy by decapitation of the fetus 3 days before death produced a reduction of LH activity in plasma and level of testosterone in the testes; the development of cranial prostatic buds was impaired although plasma levels of testosterone were unchanged. Injections of testosterone propionate (10 mg) on days 18, 19 and 20 of gestation had similar effects on testicular testosterone; this effect was not due to a direct inhibition of androgen synthesis by testosterone, but to a lowering of LH activity and suggests the existence of a feedback mechanism of testosterone on the fetal hypothalamo-pituitary axis.