Gynecomastia is the growth of abnormally large breasts in males. It is due to the excess growth of breast tissue, not excess fat tissue.

Breast development in a male

The condition may occur in one or both breasts and begins as a small lump beneath the nipple, which may be tender. The breasts often enlarge unevenly. Gynecomastia during puberty is not uncommon and usually goes away over a period of months.

In newborns, breast development may be associated with milk flow (galactorrhea). This condition usually lasts for a couple of weeks, but in rare cases may last until the child is 2 years old.

Androgens are hormones that create male characteristics, such as hair growth, muscle size, and a deep voice. Estrogens are hormones that create female characteristics. All men have both androgens and estrogens.

Changes in the levels of these hormones, or in how the body uses or responds to these hormones can cause enlarged breasts in men.

More than half of boys develop gynecomastia during puberty.

Other causes include:

• Aging
• Cancer chemotherapy
• Chronic liver disease
• Exposure to anabolic steroid hormones
• Exposure to estrogen hormone
• Kidney failure and dialysis
• Lack (deficiency) of testosterone (male hormone)
• Marijuana use
• Hormone treatment for prostate cancer
• Radiation treatment of the testicles
• Side effects of some medications (ketoconazole, spironolactone, metronidazole, cimetidine (Tagamet))

Rare causes include:

• Genetic defects
• Overactive thyroid
• Tumors

Breast cancer in men is rare. Signs that may suggest breast cancer include:

• One-sided breast growth
• Firm or hard breast lump that feels like it is attached to the tissue
• Skin sore over the breast
• Bloody discharge from the nipple

Apply cold compresses and use pain relievers ( analgesics) as your health care provider recommends if swollen breasts are also tender.

Other tips include:

• Stop taking all recreational drugs, such as marijuana
• Stop taking all nutritional supplements or any drugs you are taking for bodybuilding

Call your health care provider if:

• You have recent swelling, pain, or enlargement in one or both breasts
• There is dark or bloody discharge from the nipples
• There is a skin sore or ulcer over the breast
• A breast lump feels hard or firm

Note: Gynecomastia in children who have not yet reached puberty should always be checked by a health care provider.

Your health care provider will take a medical history and perform a physical examination.

Medical history questions may include:

• Is one or both breasts involved?
• What is the age and gender of the patient?
• What medications is the person taking?
• How long has gynecomastia been present?
• Is the gynecomastia staying the same, getting better, or getting worse?
• What other symptoms are present?

Testing may not be necessary, but the following tests may be done to rule out certain diseases:

• Blood hormone level tests
• Breast ultrasound
• Liver and kidney function studies
• Mammogram

Intervention:

If an underlying condition is found, it is treated. Your physician should consider all medications that may be causing the problem. Gynecomastia during puberty usually goes away on its own.

Breast enlargement that is extreme, uneven, or does not go away may be embarrassing for an adolescent boy. Treatments that may be used in rare situations are:

• Hormone treatment that blocks the effects of estrogens
• Breast reduction surgery

Narula HS, Carlson HE. Gynecomastia. Endocrinol Metab Clin North Am. 2007/36:497-519.

Ali O, Donohue PA. Gynecomastia. In: Kliegman RM, Stanton BF, Geme JW, Schor NF, Behrman RE, eds. Nelson Textbook of Pediatrics. 19th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 579.