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Aromatase excess syndrome
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Condition

Aromatase excess syndrome

Aromatase excess syndrome is a rare condition characterized by the overproduction of estrogen, leading to early growth spurts, short stature, and gynecomastia in males.

Overview

Aromatase excess syndrome is a condition marked by elevated levels of the female sex hormone estrogen in both males and females. While fertility is usually normal in both sexes, the condition significantly impacts physical development.

Symptoms

  • Males: Breast enlargement (gynecomastia) typically appearing in late childhood or adolescence. Affected males often experience an early growth spurt followed by premature bone maturation, resulting in short stature as an adult.
  • Females: Signs are less common but may include increased breast growth (macromastia), irregular menstrual periods, and short stature.

Causes & Risk Factors

The condition is caused by rearrangements of genetic material involving the CYP19A1 gene. This gene provides instructions for making the enzyme aromatase.

  • Enzyme Function: Aromatase converts androgens (involved in male sexual development) into various forms of estrogen.
  • Genetic Rearrangements: These rearrangements increase the activity of the CYP19A1 gene, leading to an overproduction of aromatase.
  • Physiological Impact: The resulting excess of estrogen causes the characteristic symptoms, such as gynecomastia in males and irregular cycles in females, while also accelerating bone development.

Inheritance

Aromatase excess syndrome is inherited in an autosomal dominant pattern. A genetic rearrangement involving only one copy of the CYP19A1 gene in each cell is sufficient to cause the disorder. In some instances, the condition is inherited from an affected parent, while other cases result from new (de novo) mutations in people with no family history of the disorder.

Frequently Asked Questions

Yes. Because aromatase excess syndrome follows an autosomal‑dominant pattern, first‑degree relatives have a 50 % chance of carrying the same CYP19A1 rearrangement. Targeted DNA testing can identify carriers, allowing early monitoring for signs of estrogen excess and timely intervention.
First‑line therapy is an aromatase inhibitor such as letrozole or anastrozole, dosed according to pediatric guidelines, which reduces estrogen synthesis and can halt premature bone maturation. In some cases, tamoxifen is added to block estrogen receptors. Treatment should be monitored with serial bone age X‑rays and growth‑plate assessments.
Fertility is usually preserved because gonadal function remains intact; however, excess estrogen can impair spermatogenesis in some males. A semen analysis is recommended in adolescence. Counseling should include discussion of potential need for assisted reproductive techniques if infertility arises and reassurance that normal puberty and reproductive capacity are achievable with proper hormonal management.
Diagnosis relies on a combination of clinical features (gynecomastia, early growth spurt, short adult stature) and biochemical testing. Serum estradiol is markedly elevated for age while testosterone and LH/FSH may be low‑normal. A definitive diagnosis requires molecular analysis showing a CYP19A1 gene rearrangement or duplication.
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.

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