Gynecomastia: enlarged breast tissue in men, explained
Last updated September 3, 2026.
Gynecomastia is the growth of actual breast gland tissue in males, producing a rubbery, sometimes tender mound behind the nipple, on one side or both. It is remarkably common: most newborns, over half of pubertal boys, and a large share of older men have it at some point. It is benign, but a new or changing male breast lump always deserves a proper check.
What does it feel like?
A firm, rubbery, button-like disc of tissue directly behind the nipple and areola, often tender in the early growing phase, on one or both sides. It differs from simple chest fat (pseudogynecomastia), which is soft and spread out without a defined disc. The tenderness typically fades within months even when the tissue remains. True gynecomastia has no skin changes, no nipple discharge, and no hard, irregular, fixed lump; those features point elsewhere.
Why does it happen?
The common thread is a shift in the balance between estrogen and testosterone. Puberty swings the balance temporarily (usually settling within two years). Aging lowers testosterone. Medications are a major cause: some blood-pressure and heart drugs, anti-ulcer drugs, certain antidepressants and antipsychotics, finasteride-type drugs, anabolic steroids, and cannabis and excess alcohol are all implicated. Less often: thyroid overactivity, liver or kidney disease, or hormone-producing conditions. Sometimes no cause is found.
What actually helps?
- Time: pubertal gynecomastia resolves by itself in the majority, usually within six months to two years; reassurance and review are the standard.
- Review the drivers: a medication check with your prescriber (never stop prescribed drugs on your own), cutting alcohol and cannabis, and stopping anabolic steroids are the highest-yield changes.
- Treat any underlying cause: thyroid, liver, or hormonal problems found on blood tests get treated directly.
- Weight: losing fat reduces the fatty component and the chest's appearance, though established gland tissue itself does not shrink with weight loss.
- Medication and surgery: tamoxifen helps in selected early, tender cases; long-standing (over a year) fibrosed tissue does not respond to drugs, and surgery (tissue removal, sometimes with liposuction) is the definitive option when it matters to the person.
When is it an emergency?
Gynecomastia itself never is. But features that are not typical gynecomastia need prompt review: a hard, irregular, or fixed lump; a lump not centered behind the nipple; skin dimpling or ulceration; nipple discharge, especially bloody or one-sided; or a lump that keeps growing. Male breast cancer is rare but real, and these are its warning shapes. Testicular lumps or symptoms alongside breast growth also need review. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
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Common questions
Is gynecomastia a sign of breast cancer?
Almost never. Male breast cancer is rare and looks different: typically a hard, irregular, fixed lump, often away from the nipple center, sometimes with skin dimpling, nipple inversion, or bloody discharge. Gynecomastia is a rubbery disc directly behind the nipple, often tender, often both sides. The features that should change your expectation: hardness, fixation, eccentric position, skin or nipple changes, and steady growth. Any of those turns reassurance into investigation quickly.
Will puberty gynecomastia go away?
In most boys, yes: roughly 9 in 10 cases of pubertal gynecomastia resolve without treatment, typically within six months to two years as hormones stabilize. Tenderness fades first. While it lasts, it is embarrassing and that matters: loose tops, avoiding chest-tight clothing, and knowing it is temporary carry most boys through. Persistent cases beyond two years, severe cases, or major distress are reasons to see a specialist rather than just wait longer.
Which medications cause it?
The list is long and worth a proper review: spironolactone and some other blood-pressure drugs, cimetidine and other ulcer treatments, certain antidepressants and antipsychotics, finasteride and dutasteride (hair-loss and prostate drugs), some chemotherapy and HIV treatments, and anabolic steroids. Cannabis and heavy alcohol are also implicated. Do not stop a prescribed medication on your own; the right move is a medication review where the prescriber weighs alternatives. Often a swap exists.
Does losing weight fix it?
It depends what the mound is made of. Chest fat (pseudogynecomastia) shrinks with weight loss and responds well to it. True gynecomastia is gland tissue, which does not shrink with dieting; losing weight improves the overall chest contour but the rubbery disc behind the nipple stays. Many men have a mix of both. An examination (sometimes with ultrasound) tells which predominates, and therefore whether the gym or a different approach will actually change the picture.
Can it be treated without surgery?
Sometimes, if caught early. In the active, tender, growing phase (roughly the first year), medications like tamoxifen can shrink gland tissue substantially in some men and are used off-label for this. Once the tissue has been present over a year or two, it fibroses, and no tablet shrinks it; surgery (usually tissue excision through a small incision around the areola, often combined with liposuction) is then the definitive option. Surgery results are generally good, with recurrence uncommon when the cause is addressed.
Why is it only on one side?
One-sided gynecomastia is common and usually still benign; the hormone-driven tissue does not grow symmetrically. The evaluation is the same as for two-sided cases: confirm it is the classic rubbery disc behind the nipple, review medications and substances, and check blood tests if anything is atypical. One-sidedness alone is not a red flag. The features that matter are hardness, fixation, position away from the nipple, skin or nipple changes, and growth, wherever they occur.