Differential Responsiveness of Pregnant and Nonpregnant Guinea Pigs to the Masculinizing Action of Testosterone Propionate

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Abstract
The response of pregnant and nonpregnant guinea pigs to the masculinizing action of testosterone propionate was investigated. Testosterone propionate will not induce malelike mounting nor clitoral hypertrophy in pregnant animals to the extent that these changes are induced in nonpregnant females. This inhibitory or “protective” action of pregnancy is lost within 3 days after parturition. In nonpregnant females, progesterone inhibited the testosterone propionate induction of mounting behavior, but not clitoral hypertrophy. A differential responsiveness of clitoral tissues and the tissues mediating mounting behavior is thought to be involved. Attention is directed to reports indicating that most pregnant women given androgens or gestagens during pregnancy did not become virilized, although these substances were sufficiently potent to masculinize their female fetuses.