What Is Gynecomastia?
Print PageGynecomastia is abnormally large breast development in a male due to swelling of the mammary gland. It can involve only one breast or both. The rate of breast development is often uneven, so the breasts may be different sizes. Breast enlargement may be accompanied by breast pain (mastalgia). True gynecomastia is caused by a hormonal imbalance. The affected male produces too much estradiol, the female breast growth hormone. Pseudogynecomastia is breast enlargement caused by fat deposition over the entire chest, not localized to the breasts.
Newborn and pubescent boys often
develop temporary breast enlargement.