5-alpha Reductase Deficiency

View a glossary of key terms and definitions commonly used in discussions about sex development. 

What is 5-alpha Reductase Deficiency?

5-alpha Reductase Deficiency (5ARD) is a genetic condition that affects people with 46,XY chromosomes and testes. These individuals produce normal amounts of testosterone but cannot convert it into a stronger hormone called DHT. Because of this, babies with 5ARD may have external genitalia that look more like female or nonbinary genitalia at birth. During puberty, their testosterone levels increase, leading to changes like more muscle mass, a deeper voice, and genital growth.

What Causes 5-alpha Reductase Deficiency?

5ARD is caused by a change in the SRD5A2 gene, which affects an enzyme called steroid 5-alpha reductase 2. This enzyme usually converts testosterone into DHT, which is important for developing male genitalia before birth. The condition can be inherited from parents or can happen by chance in one person.

How is 5-alpha Reductase Deficiency Diagnosed?

Doctors diagnose 5ARD when a baby with female-like or nonbinary genitalia has tests that show 46,XY chromosomes and specific hormone levels (high testosterone and low DHT). In older kids or teens, doctors might notice the condition when someone who looked more female at birth starts to develop changes typical for males during puberty. Tests will show the same hormone pattern as in younger children.

How is 5-alpha Reductase Deficiency Treated?

Treatment for 5-alpha Reductase Deficiency depends on what each person needs and may include:

• Psychological support: Helps individuals and their families deal with the condition.
• Hormone treatments: Estrogen or testosterone supplements, or medicines that block hormones, might be used during puberty.
• Surgery: Surgery on the genitalia is not usually urgent and is discussed based on what the person wants and needs.