This information is provided by the National Institutes of Health (NIH) Genetic and Rare Diseases Information Center (GARD).
5-alpha reductase deficiency is an inherited condition that primarily affects male 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), which is critical for male sexual development. Most are born with external genitalia that appear female. In other cases, affected individuals may have ambiguous genitalia. Others may have genitalia that appear predominantly male, often with an unusually small penis (micropenis) and the urethra opening on the underside of the penis (hypospadias). This condition is caused by mutations in the SRD5A2 gene and is inherited in an autosomal recessive pattern.
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