Medical Specialties: Endocrinology, Internal medicine

Clinical Definition

Gynecomastia is an abnormal development of the mammary glands in males. The condition is different from an enlarged breast area due to obesity and an increase in adipose tissue. Gynecomastia is usually benign and may develop unilaterally or bilaterally. 

In Our Own Words

Gynecomastia is the abnormal enlargement of breasts in men or boys—enlargement that’s not due to obesity.


Androgens are hormones that promote male characteristics while estrogen spurs the development of female characteristics; men have both types of hormones. Gynecomastia can develop due to hormonal imbalances and this occurs most commonly during puberty; as many as 50 percent of boys may have some breast enlargement during puberty. Although the condition is not usually serious, it can create issues with self-esteem and may be debilitating psychologically.


When not an awkward sign of puberty, gynecomnastia may stem from hormonal imbalance from a variety of other causes including drugs, some herbal products, cirrhosis and liver problems.

Relevant Conditions
Side Effects
  • Breast tissue enlargement
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  • University of Maryland Medical Center. "Gynecomastia." Assessed September 2013.
  • NYU Langone Medical Center. "Gynecomastia." Assessed September 2013.
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