A 5-alpha reductase deficiency at birth causes ambiguous to female-type external genitalia. The male has undescended testes. The deficiency essentially prevents testosterone from becoming dihydrotestosterone (DHT). Now the penis-at-12 syndrom itself occurs around puberty when the high levels of testosterone overcome the requirement of DHT...the clitoris enlarges, alas, "penis-at-12".
by eleven April 28, 2003