HomeGeneticsConditionAromatase deficiency
Back to Condition
Aromatase deficiency
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Condition

Aromatase deficiency

Aromatase deficiency is a rare condition characterized by significantly reduced levels of the female sex hormone estrogen and increased levels of the male sex hormone testosterone, impacting sexual development, bone health, and metabolism in affected individuals.

Overview

Aromatase deficiency is a condition characterized by reduced levels of the female sex hormone estrogen and increased levels of the male sex hormone testosterone.

Frequency

The prevalence of aromatase deficiency is unknown; approximately 20 cases have been described in the medical literature.

Symptoms

Females with aromatase deficiency have a typical female chromosome pattern (46,XX) but are born with external genitalia that do not appear clearly female or male. These individuals typically have primary amenorrhea, but develop ovarian cysts early in childhood, which impair the release of egg cells from the ovaries (ovulation). In adolescence, most affected females do not develop secondary sexual characteristics, such as breast growth and menstrual periods. They tend to develop acne and excessive body hair growth (hirsutism).

Men with this condition have a typical male chromosome pattern (46,XY) and are born with male external genitalia. Some men with this condition have decreased sex drive, abnormal sperm production, or testes that are small or undescended (cryptorchidism).

There are other features associated with aromatase deficiency that can affect both males and females. Affected individuals are abnormally tall because of excessive growth of long bones in the arms and legs. The abnormal bone growth results in slowed mineralization of bones (delayed bone age) and thinning of the bones (osteoporosis), which can lead to bone fractures with little trauma. In affected individuals, the body does not respond correctly to the hormone insulin, so people with aromatase deficiency can have abnormally high blood sugar (glucose), a condition known as hyperglycemia. In addition, people with aromatase deficiency can have excessive weight gain and a fatty liver.

Women who are pregnant with fetuses that have aromatase deficiency often experience mild symptoms of the disorder even though they themselves do not have the disorder. These women may develop hirsutism, acne, an enlarged clitoris (clitoromegaly), and a deep voice. These features can appear as early as 12 weeks of pregnancy and go away soon after delivery.

Causes & Risk Factors

Mutations in the CYP19A1 gene cause aromatase deficiency. The CYP19A1 gene provides instructions for making an enzyme called aromatase. This enzyme converts a class of hormones called androgens, which are involved in male sexual development, to different forms of estrogen. In females, estrogen guides female sexual development before birth and during puberty. In both males and females, estrogen plays a role in regulating bone growth and blood glucose levels. During fetal development, aromatase converts androgens to estrogens in the placenta, which is the link between the mother's blood supply and the fetus. This conversion in the placenta prevents androgens from directing sexual development in female fetuses. After birth, the conversion of androgens to estrogens takes place in multiple tissues.

CYP19A1 gene mutations that cause aromatase deficiency decrease or eliminate aromatase activity. A shortage of functional aromatase results in an inability to convert androgens to estrogens before birth and throughout life. As a result, there is a decrease in estrogen production and an increase in the levels of androgens, including testosterone. In affected individuals, these abnormal hormone levels lead to impaired female sexual development, unusual bone growth, insulin resistance, and other signs and symptoms of aromatase deficiency. In women who are pregnant with an affected fetus, excess androgens in the placenta pass into the woman's bloodstream, which may cause her to have temporary signs and symptoms of aromatase deficiency.

Learn more about the gene associated with Aromatase deficiency

  • CYP19A1

Inheritance

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

Other Names for This Condition

  • 46,XX disorder of sex development (DSD) due to placental aromatase deficiency
  • Estrogen synthetase deficiency
  • Oestrogen synthetase deficiency
  • Placental aromatase deficiency

Frequently Asked Questions

Management of aromatase deficiency primarily involves hormone replacement therapy. Females typically receive estrogen replacement therapy to induce puberty, develop secondary sexual characteristics, prevent osteoporosis, and regulate menstrual cycles. Males may receive testosterone replacement therapy to promote normal male puberty, maintain bone density, and address symptoms like decreased sex drive. Treatment plans are individualized and adjusted throughout life by an endocrinologist.
In females with aromatase deficiency, a key sign at birth is external genitalia that appear ambiguous, not clearly female or male. Later in childhood, girls may develop ovarian cysts. Both males and females with the condition tend to grow abnormally tall due to excessive long bone growth and may show signs of delayed bone age. For males, signs might be less obvious at birth but can include undescended testes or small testes.
Fertility can be significantly impacted by aromatase deficiency. Females typically experience primary amenorrhea and impaired ovulation due to ovarian cysts, making natural conception difficult or impossible. Males may have abnormal sperm production or small/undescended testes, leading to infertility. While natural conception is rare, assisted reproductive technologies may be an option for some individuals, depending on their specific circumstances. Genetic counseling is important to discuss reproductive options and risks.
Individuals with aromatase deficiency are at significant risk for poor bone mineralization, leading to delayed bone age and osteoporosis, which can result in bone fractures from minor trauma. This is due to the lack of estrogen, which is crucial for bone health in both sexes. Bone health is addressed through hormone replacement therapy, which helps improve bone density. Regular bone density scans (DEXA scans) are recommended to monitor bone health, along with adequate calcium and vitamin D intake.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

kontakt@hittavard.se

Ⓒ 2024. Alla rättigheter förbehålls av juxt ab

Sök
Om ossVillkor och policyVanliga frågorKontakta oss