Summary

• May be unilateral or bilateral, painful, or asymptomatic. Male breast enlargement is benign in 99% of cases.
• Results from relative estrogen excess or relative testosterone deficiency resulting in a high estrogen-to-testosterone ratio.
• Physiologic gynecomastia occurs in the newborn period, during puberty, and with aging and obesity.
• Many drugs, environmental exposures, illnesses, and some genetic conditions increase the risk for gynecomastia.
• Most cases require no specific treatment. Therapies for persistent pain or embarrassment include anti-estrogen therapy such as tamoxifen, androgens, or surgery (liposuction or mammoplasty).