5-alpha reductase deficiency

5-alpha reductase deficiency is a condition that affects sexual development before birth and during puberty. 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 hormone called dihydrotestosterone (DHT). DHT has a critical role in male sexual development, and a shortage of this hormone disrupts the formation of the external sex organs before birth.

Many people with 5-alpha reductase deficiency have external genitalia that appears female. In other cases, affected infants have male-typical external genitalia, often an unusually small penis (micropenis) and the urethra opening on the underside of the penis (hypospadias). Still other affected infants have external genitalia do not look clearly male or clearly female.

During puberty, an increase in the levels of male sex hormones leads to the development of some secondary sex characteristics, such as increased muscle mass, deepening of the voice, development of pubic hair, and a growth spurt. The penis and scrotum (the sac of skin that holds the testes) may grow larger. People with 5-alpha reductase deficiency do not develop much facial or body hair. Most affected individuals are unable to have biological children (infertile) without assisted reproduction.