17-beta hydroxysteroid dehydrogenase 3 deficiency

17-beta hydroxysteroid dehydrogenase 3 deficiency is a condition that affects male sexual development. People with this condition are genetically male, with one X and one Y chromosome in each cell, and they have male gonads (testes). Their bodies, however, do not produce enough of a male sex hormone (androgen) called testosterone. Testosterone has a critical role in male sexual development, and a shortage of this hormone disrupts the formation of the external sex organs before birth.

Most people with 17-beta hydroxysteroid dehydrogenase 3 deficiency are born with external genitalia that appear female. In some cases, the external genitalia do not look clearly male or clearly female. Still other affected infants have genitalia that appear predominantly male, often with an unusually small penis (micropenis) or the urethra opening on the underside of the penis (hypospadias).

During puberty, people with this condition develop some male secondary sex characteristics, such as increased muscle mass, deepening of the voice, and development of male pattern facial and body hair. In addition to these changes typical of adolescent boys, some affected individuals may also experience breast enlargement (gynecomastia). Despite having testes, people with this disorder are generally unable to father children (infertile).