Role of testosterone and its metabolites in the differentiation of the mammary gland in rats.

The capacity of various androgens to virilize the differentiating mammary gland in the female rat fetus has been determined. Testosterone, 5alpha-androstane-3alpha, 17beta-diol (3alpha-diol), and dihydrotestosterone (DHT) virilize the anlagen of the mammary gland by suppressing nipple formation but 5alpha-androstane-3beta, 17beta-diol, androsterone, and dehydroepiandrosterone sulfate do not affect female mammary differentiation. However, unlike the genitalia and wolffian ducts of the female rat fetus in which the masculinizing potency of DHT and 3alpha-diol is greater than that of testosterone, testosterone is more potent than its metabolites DHT and 3alpha-diol, in virilizing the mammary gland. The results suggest that testosterone is the fetal androgen mediating masculine development of the mammary gland.