Gynecomastia can usually be diagnosed from a physical exam and medical history. They may last up to 2 years, but they tend to go away within the first year. Breast buds are common in adolescent boys during puberty. Boys may have a breast bud on one or both sides about the size of a nickel or quarter. In addition to having enlarged breasts, men or boys with gynecomastia may notice their breasts feel rubbery or firm.

Antianxiety and antidepressant medicines (such as diazepam and tricyclic antidepressants).Antiandrogen drugs (such as flutamide, cyproterone, and spironolactone).Chemotherapy drugs, especially alkylating agents, a family of anticancer drugs that interfere with cell DNA and inhibit cancer cell growth.Medicines used to treat epilepsy (such as phenytoin ).Medicines used to treat ulcers (such as cimetidine).Steroids, such as prednisone or dexamethasone.Use of certain medicines may also cause gynecomastia, including: Alcohol, marijuana, methamphetamine, and heroin use also may cause gynecomastia. In adult males, gynecomastia is usually caused by another condition, such as liver or lung cancer, cirrhosis of the liver, overactive thyroid, or by hormone problems, such as cancer of the pituitary gland, adrenal glands, or testicles. It usually goes away within 6 months to 2 years. Gynecomastia occurs in many boys during early puberty to middle puberty. In teen boys, gynecomastia is caused by the hormonal changes of puberty. The buds may last up to 2 years, but they tend to go away within the first year. In preteen boys, gynecomastia can also be caused by an estrogen-producing tumor. Breast buds tend to go away gradually by 6 months of age, but they can last longer in some babies. In newborns, gynecomastia is caused by estrogen from the mother. Gynecomastia can occur in babies, teen boys, and older men. In response to too much estrogen (a female hormone) or too little testosterone (a male hormone), the glandular tissue of the breast swells and forms a breast bud (enlarged breast). Gynecomastia is overdevelopment of the male breast.