Gynecomastia is the growth of breast tissue in males. It's a benign condition that usually results from an imbalance in the sex hormones estrogen and testosterone.
Men generally have some amount of estrogen in their bodies, similar to the way that women usually have some level of testosterone. But too much estrogen in a man's body relative to the amount of testosterone can cause breast tissue to swell.
More than half of boys have some degree of gynecomastia during puberty, according to the National Institutes of Health (NIH). Though gynecomastia itself is usually harmless, it can be associated with some health conditions, including substance abuse, certain diseases and the use of some medications.
In addition to boys going through puberty, gynecomastia is also seen in newborn boys (due the effect of their mothers' estrogen) and is common among men older than 50, according to the Mayo Clinic. The condition may be seen in one or both breasts, and the tissue growth often occurs unevenly.
When gynecomastia develops, it may be painless, or it can be accompanied by tenderness, pain or discharge from one or both nipples. In most cases, the condition goes away on its own after a few weeks or months, though treatment may be sought for gynecomastia that lasts longer.
Gynecomastia and drugs
A 2012 report in the journal Expert Opinion on Drug Safety estimated that drugs — prescription, recreational and illegal — cause up to 25 percent of gynecomastia cases. Anabolic steroid use (common among bodybuilders) is frequently associated with gynecomastia.
Marijuana, heroin and alcohol use have also been linked with the development of male breasts (sometimes referred to as "man boobs"). Cirrhosis of the liver — often seen among people who abuse alcohol — can alter hormone levels and lead to gynecomastia.
Other drugs that have been cited as leading to gynecomastia include anti-androgens used to treat prostate cancer such as finasteride (Propecia), anti-anxiety drugs such as diazepam (Valium), calcium-channel blockers, ulcer medications such as cimetidine (Tagamet), antibiotics, tricyclic antidepressants and some AIDS medications such as the antiretroviral efavirenz (Sustiva).
Health conditions and gynecomastia
Gynecomastia has been associated with conditions that interfere with hormone production such as Klinefelter syndrome, hyperthyroidism, liver problems, kidney failure and pituitary insufficiency.
Testicular tumors and trauma or infection of the testes can cause gynecomastia, as can radiation treatment of the testicles. Normal aging, and the associated drop in hormone levels, has also been cited as a cause of gynecomastia.
Certain plant-based compounds, such as tea tree oil or lavender oil, that mimic estrogen can have estrogen-like effects on a man's body, leading to gynecomastia.
Treatment of gynecomastia
In most cases of gynecomastia, no treatment is needed as the condition often regresses on its own when hormone levels return to normal. When drugs, alcohol, prescription medication or other factors cause gynecomastia, stopping these (such as switching to a different medication) will also resolve the condition.
In some cases, surgery to remove the breast tissue may be appropriate for men who have a lot of tissue built up, or if they've had gynecomastia for a long time. Certain drugs that can block the effect of estrogens have also proven effective.
For men — especially teenagers — who are concerned about gynecomastia and the embarrassment it can cause, counseling is sometimes recommended.
Sign up for the Live Science daily newsletter now
Get the world’s most fascinating discoveries delivered straight to your inbox.