What Causes Gynecomastia in Adults? Every Cause, Explained

Quick answer

In adults, doctors most often find normal age-related hormone changes or no clear cause, about a quarter each. Medicines and other substances cause 10 to 25% of cases, and that's the group most often fixable. Liver disease, low testosterone, thyroid problems, kidney failure and, rarely, tumors make up the rest. Because some causes are treatable, adult gyno deserves a checkup.

On this page

1. Why adult gyno needs a reason
2. What doctors find in men with gyno
3. Normal hormone changes
4. No clear cause
5. Medicines and substances
6. Weight
7. Low testosterone
8. Liver and kidney disease
9. Thyroid and tumors
10. Which causes can be fixed
11. Questions
12. Sources

Why adult gyno needs a reason

In teenagers, gyno is usually just puberty, and doctors are happy to watch it. In adults, it's different. American Family Physician advises that symptoms lasting longer than one to two years suggest a cause other than normal development, and that every man should have his medicines, supplements and drug use reviewed. Most adult gyno is still harmless. But a few causes need treatment in their own right, and a few can be reversed, which can make the gyno go away.

What doctors find in men with gyno

1. Normal hormone changes 25%
2. No clear cause 25%
3. Medicines and other substances 10 to 25%
4. Liver cirrhosis 8%
5. Low testosterone from the testicles 8%
6. Other causes 6%
7. Tumors 3%
8. Low testosterone from the brain's signal 2%
9. Overactive thyroid 2%
10. Kidney failure 1%

Source: Dickson, American Family Physician, 2012, Table 1. The medicines figure is a range; the bar shows its top end.

Normal hormone changes

A quarter of cases are what doctors call physiologic: normal changes in the hormone balance. In adults, that mostly means age. As men get older, free testosterone falls, and American Family Physician says about 65% of men between 50 and 80 have some gyno. It's not a disease; it's part of how the balance shifts over time. More in gynecomastia in older men.

No clear cause

Another quarter are idiopathic: the doctors look, the tests are normal, and nothing explains it. That's frustrating, but it's also reassuring. It means nothing serious was found.

Medicines and substances

This is the slice to pay attention to, because it's the one most often fixed. A long list of prescriptions can cause gyno, from spironolactone and finasteride to some heart, stomach and psychiatric medicines, as well as anabolic steroids, marijuana, alcohol, and some herbal products. American Family Physician says stopping the cause often makes the tissue shrink within about three months. The full list is in medications that cause gynecomastia, and steroids have their own page: steroid gyno.

Never stop a prescription on your own. Bring your list to your doctor.

Weight

Body fat matters in two ways. First, chest fat can look like gyno without being it, which doctors call pseudogynecomastia: see gyno vs chest fat. Second, American Family Physician notes that the aromatase activity linked to obesity raises circulating estrogen, which can tip the balance toward real gland growth.

Low testosterone

Low testosterone can start in the testicles themselves, which doctors call primary hypogonadism (8% of cases), or in the brain's signal to them, called secondary hypogonadism (2%). Either way, less testosterone means estrogen has an easier time. Klinefelter syndrome, a genetic condition, is one cause of the testicular kind.

Liver and kidney disease

Cirrhosis accounts for about 8%. A damaged liver raises the amount of a protein that binds testosterone, which American Family Physician says contributes to higher estrogen levels. Heavy drinking is a common road to cirrhosis, and alcohol is on the substance list too. Long-term kidney failure accounts for about 1%.

Thyroid and tumors

An overactive thyroid causes about 2%. Tumors cause about 3%: rare tumors of the testicles, adrenal glands or elsewhere that make hormones. That's why a doctor checks the testicles during the exam and may order more tests if anything is unusual.

Which causes can be fixed

Based on American Family Physician, 2012. Gyno that's been there over a year may not shrink even when the cause is fixed.

Questions people ask

Sources

1. Dickson G. Gynecomastia. American Family Physician, 2012;85(7):716-722
2. Lemaine V, Cayci C, Simmons PS, Petty P. Gynecomastia in adolescent males. Seminars in Plastic Surgery, 2013
3. Cigna. Coverage Policy 0195, Gynecomastia Surgery (lists Klinefelter syndrome)

Medical facts last checked against these sources on November 2, 2026.

Medical disclaimer. I'm a guy who has lived with gyno, not a doctor. This page explains what published medical sources say, in plain words, so you can have a better conversation with your own doctor. It isn't medical advice, a diagnosis or a treatment plan. Don't start, stop or change any medication without talking to a doctor. If something on your chest is changing fast, hurts, or leaks fluid, get it checked.

Comments

No comments yet. If this matches what you're going through, say so. It helps the next guy.

Leave this empty

Name (a first name or nickname is fine) Your comment

Comments are read before they appear. Please don't post anything you wouldn't want public, like medical records or your full name.

Post comment

Keep reading

• Understand it Medications That Cause Gynecomastia: The List, and What to Do
• Understand it Gynecomastia Tests: What Your Doctor Checks, and Why
• Understand it Gynecomastia in Older Men: Why It Shows Up After 50
• Understand it Steroid Gyno: Why Steroids Cause It, and Why It Often Stays