Forming genitals in boys requires complex dance between genes and hormones

The most common congenital disorders of all, especially in baby boys, are differences in a newborn's sexual anatomy that is not standard female or male. In boys, they include undescended testicles, misplaced urethras, and improperly developed internal organs. Some of these disorders may be treated with surgery and some also with hormonal supplementation. Scientists are troubled because the incidence of these disorders is increasing, especially in developed countries. While causes are unknown, researchers suspect that endocrine disruptors from environmental contaminants may be involved. "It's hard to know how something goes wrong if you don't know how it goes right," says Joan Jorgensen , a professor of comparative biosciences in the University of Wisconsin-Madison School of Veterinary Medicine. So, Jorgensen, lead author Anbarasi Kothandapani, and others have set out to understand how functional reproductive systems are formed.