Gynecomastia

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What is gynecomastia?

Gynecomastia is overdevelopment of the male breast. The glandular tissue of the breast swells, usually in response to an excess of the female hormone estrogen or a lack of testosterone, a male hormone. It occurs in babies, teen boys, and older men.

What causes gynecomastia?

In newborns, gynecomastia is caused by estrogen from the mother. Breast buds are common in baby boys. Breast buds tend to go away gradually by 6 months of age, but they can last longer in some babies.

In preteen boys, breast buds are common during puberty. The buds may last up to 2 years, but they tend to go away within the first year. In a few cases, it has been linked to regular use of lavender or tea tree oil in certain lotions or oils.¹ Gynecomastia can also be caused by an estrogen-producing tumor.

In teen boys, gynecomastia is caused by the hormonal changes of puberty. Gynecomastia occurs in more than 60% of boys in early puberty to middle puberty. It goes away in 70% of boys within 1 year and 90% of boys in 2 years.

When gynecomastia occurs in adult males, it 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. Alcohol, marijuana, methamphetamine, and heroin use also may cause gynecomastia.

Use of certain medicines may also cause gynecomastia, including:

• Steroids, such as prednisone or dexamethasone.
• Medicines used to treat ulcers (such as cimetidine).
• Medicines used to treat epilepsy (such as phenytoin [Dilantin]).
• Digitalis and other heart medicines.
• Chemotherapy drugs, especially alkylating agents, a family of anticancer drugs that interfere with cell DNA and inhibit cancer cell growth.
• Antiandrogen drugs (such as flutamide, cyproterone, and spironolactone).
• Antianxiety and antidepressant medicines (such as diazepam [Valium] and tricyclic antidepressants).
• Products containing tea tree oil or lavender oil.¹

What are the symptoms?

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

How is gynecomastia diagnosed?

Gynecomastia can usually be diagnosed from a physical examination and medical history. In most cases, tests are not necessary. But if the breast lump is unusually large, one-sided, tender, or hard and fixed, a biopsy may be done to rule out other problems.

Any man who finds a one-sided breast lump should let his doctor know if he has close relatives who have had breast cancer (mother, sister, or daughter). If there is any concern about cancer, a lump can be checked with a biopsy or surgery.

How is it treated?

Gynecomastia in babies and teens normally does not require treatment and will usually go away on its own. If caused by medicine or disease, stopping the medicine or treating the disease will often cure the gynecomastia. If caused by a lack of testosterone and increase in estrogen, hormonal treatment may be prescribed.

• Growth and Development, Ages 1 to 12 Months
• Growth and Development, Ages 15 to 18 Years
• Growth and Development, Newborn

Citations

1. Henley DV, et al. (2007). Prepubertal gynecomastia linked to lavender and tea tree oils. New England Journal of Medicine, 356(5): 479–485.