What is gynecomastia?

Gynecomastia is a condition in which firm breast tissue forms in males. The breast tissue is usually less than 1-1/2 inches across and is located directly under the nipple. Gynecomastia may be present on one side or on both sides. This condition may make the breast tender.

Some men and boys have fat on their chests that makes it look like they have breasts. This condition is called pseudogynecomastia (false gynecomastia). It is not the same thing as gynecomastia.

What causes gynecomastia?

Gynecomastia is usually caused by changes in hormones at puberty or as part of aging. Hormones are chemicals produced by the glands of the body, such as the thyroid gland, the testes and the ovaries. Gynecomastia may be caused by changes in the balance of 2 hormones, estrogen and testosterone. In rare cases, gynecomastia is caused by prescription drugs, over-the-counter medicines, illegal drugs, tumors or disease.