Gynecomastia, commonly called “gyno,” is caused by an imbalance between estrogen and testosterone in a man’s body. When estrogen levels rise relative to testosterone, or when testosterone drops, estrogen binds to receptors in breast tissue and triggers the growth of glandular and ductal cells. This isn’t the same as having a larger chest from body fat. Gynecomastia involves actual breast gland tissue, which feels firm or rubbery beneath the nipple, while fat deposits alone (sometimes called pseudogynecomastia) feel soft and uniform.
The Hormonal Mechanism Behind It
Every man produces some estrogen, just as every woman produces some testosterone. Problems arise when the ratio tips. Estrogen stimulates breast tissue to grow, while testosterone counteracts that signal by inhibiting growth and differentiation. When something disrupts the balance, whether by boosting estrogen, lowering testosterone, or both, breast gland cells start multiplying.
One key player is an enzyme called aromatase, which converts testosterone into estrogen. When aromatase activity is higher than normal, it produces excess estrogen locally in the breast tissue while also reducing the testosterone available to oppose it. This double effect makes overactive aromatase one of the most common biological drivers of gyno across all age groups.
Puberty Is the Most Common Trigger
If you’re a teenager dealing with gyno, you’re far from alone. Estimates of how many adolescent boys develop noticeable breast tissue range widely, from about 4% to as high as 60%, depending on how strictly it’s measured. The reason is timing: at the start of puberty, estrogen levels spike before testosterone catches up, creating a temporary window where the ratio favors breast tissue growth.
The good news is that 75 to 90% of pubertal gynecomastia resolves on its own within one to three years as testosterone production ramps up and the hormonal balance stabilizes. Most cases clear in under a year. If breast tissue persists well beyond puberty, it may become fibrotic (scar-like), which makes spontaneous resolution less likely.
Medications That Can Cause Gyno
Drugs are one of the most identifiable causes. Some medications shift the hormone balance directly, while others do it through mechanisms that aren’t fully understood. The most well-documented culprits include:
- Spironolactone, a blood pressure and fluid-retention drug. It causes bilateral breast enlargement that is dose-dependent, meaning higher doses carry greater risk.
- Finasteride, used for hair loss and prostate enlargement. It blocks the conversion of testosterone to its more potent form, which can shift the estrogen-to-androgen ratio.
- Calcium channel blockers like amlodipine, diltiazem, nifedipine, and verapamil, all prescribed for high blood pressure or heart conditions.
- Ketoconazole, an antifungal that at higher doses can suppress testosterone production.
- Certain psychiatric medications, including some tricyclic antidepressants and anti-anxiety drugs.
If gyno appears shortly after starting a new medication, that timing is a strong clue. In many cases, switching to an alternative drug allows the tissue to regress, though this depends on how long the enlargement has been present.
Anabolic Steroids and Recreational Drugs
Anabolic steroids are one of the most common causes of gyno in younger men who wouldn’t otherwise be at risk. It seems counterintuitive, since steroids are synthetic testosterone, but the body responds to the flood of androgens by converting a portion into estrogen through aromatization. Therapeutic doses of testosterone can do the same thing. Even non-aromatizable steroids like certain synthetic androgens have been linked to breast tissue growth through other, less understood pathways.
Marijuana acts differently. It appears to block androgen receptors, which weakens testosterone’s ability to counteract estrogen in breast tissue. Alcohol, heroin, and amphetamines have also been associated with gynecomastia, though the exact mechanisms for some of these substances remain unclear. Heavy alcohol use in particular compounds the problem when it damages the liver, which plays a central role in hormone metabolism.
Health Conditions That Shift Hormones
Several chronic diseases create the kind of sustained hormonal disruption that leads to gyno. Liver cirrhosis is a classic example. The liver is responsible for breaking down estrogen, so when it’s damaged, estrogen accumulates in the bloodstream. Medications used to treat liver disease can add to the effect.
Kidney failure is another significant cause. About half of men on dialysis develop gynecomastia due to the hormonal shifts that come with impaired kidney function. Conditions that directly affect the testicles, such as infections, injuries, or certain genetic conditions, reduce testosterone production and tilt the balance toward estrogen. Thyroid disorders and tumors of the adrenal glands, testicles, or pituitary gland can also trigger abnormal hormone levels, though these are less common.
Aging and Declining Testosterone
Gyno has a third peak later in life. In a study of hospitalized men, the overall prevalence was 65%, with the highest rate of 72% in men aged 50 to 69. Even in the 70 to 89 age group, 47% had detectable breast tissue. The primary driver is the natural decline in testosterone production that begins around age 30 and accelerates after 50. As testosterone falls, the relative influence of estrogen increases, and body fat, which contains aromatase, tends to increase with age, further converting remaining testosterone into estrogen.
True Gyno vs. Chest Fat
Not every case of a fuller male chest involves glandular tissue. Pseudogynecomastia is simply fat deposits in the chest area, common in men who are overweight. The practical difference matters because pseudogynecomastia responds to weight loss, while true gynecomastia does not. On a physical exam, glandular tissue feels like a firm, disc-shaped mass directly behind the nipple, while fat feels soft and blends into the surrounding chest. When there’s any uncertainty, ultrasound imaging can distinguish the two.
Many men have a combination of both, with glandular tissue at the center and fatty tissue around it. This mixed presentation is especially common in older men and those who carry excess weight.
When Treatment Becomes Necessary
The first step is always identifying and addressing the underlying cause. If a medication is responsible, adjusting or stopping it may be enough. If a hormonal condition is driving the growth, treating that condition can allow regression. Pubertal gyno in teenagers typically warrants nothing more than reassurance and monitoring.
Surgery enters the picture when the tissue has been present long enough to become fibrotic, when the underlying cause has been treated but the breast tissue remains, or when the condition is causing significant physical discomfort or psychological distress. The approach depends on severity. Mild cases (tissue under about 250 grams with no sagging) can often be treated with liposuction alone or minor excision through a small incision at the edge of the areola. Moderate cases may combine liposuction with gland removal. Severe cases involving significant tissue volume and skin sagging may require more extensive skin removal and repositioning of the nipple.
Tissue that has been present for over a year becomes increasingly fibrous and less likely to resolve without surgery. This is why persistent gyno in adults, particularly beyond the two-year mark, is generally considered a candidate for surgical correction if it’s causing problems.