Gynecomastia happens when the balance between estrogen and testosterone shifts in your body. Males naturally produce small amounts of estrogen alongside testosterone, and when estrogen rises relative to testosterone, or testosterone drops, breast gland tissue can grow. This is extremely common: depending on age group and how it’s measured, somewhere between 35% and 69% of adolescent boys experience it during puberty alone. Understanding why it’s happening to you depends on your age, medications, lifestyle, and overall health.
How the Hormonal Shift Works
Your body is constantly maintaining a ratio between testosterone and estrogen. Testosterone keeps male breast tissue from developing, while estrogen promotes its growth. Gynecomastia doesn’t require abnormally high estrogen on its own. It just requires estrogen to be high relative to testosterone. That shift can happen in two directions: something lowers your testosterone, blocks its effects, or something raises your estrogen levels.
The tissue itself is glandular, not just fat. True gynecomastia feels firm and springy under the nipple, often like a rubbery disk. It can show up on one side or both, and the area may feel tender or sensitive to touch. This is different from pseudogynecomastia, where excess body fat creates a similar appearance but the tissue is soft, evenly distributed, and typically painless.
Puberty Is the Most Common Cause
If you’re a teenager, this is likely the explanation. During puberty, hormone levels fluctuate dramatically before settling into adult ranges. Estrogen can temporarily spike or testosterone production can lag, creating the exact imbalance that triggers breast tissue growth. Studies of large populations consistently find that roughly one in three to two in three adolescent boys develop some degree of gynecomastia during this window.
The good news is that pubertal gynecomastia typically resolves on its own as hormone levels stabilize. For most boys, the tissue shrinks within a few months to a couple of years without any treatment. If it persists well beyond puberty, that’s worth bringing up with a doctor, since longer-lasting tissue can become more fibrous and less likely to disappear without intervention.
Medications That Cause It
Medications account for an estimated 10% to 25% of all gynecomastia cases. Several drug classes are well-documented triggers, and the mechanisms vary. Some increase estrogen levels directly. Others block testosterone’s effects. Some raise prolactin, a hormone that stimulates breast tissue.
The medications with the strongest evidence include:
- Spironolactone, a blood pressure and fluid-retention drug that has anti-androgen effects
- Finasteride and dutasteride, used for hair loss and prostate enlargement
- Estrogen-based medications, including some prostate cancer treatments
- Ketoconazole, an antifungal that interferes with testosterone production
- Opioid painkillers, which can suppress testosterone over time
- Certain antipsychotics like risperidone, which raise prolactin levels
- Proton pump inhibitors like omeprazole, used for acid reflux
If you started a new medication in the months before noticing breast changes, that connection is worth exploring. Stopping or switching the drug often reverses the growth, though this should be done with medical guidance rather than abruptly.
Anabolic Steroids and Recreational Drugs
Anabolic steroid use is one of the most recognized causes of gynecomastia outside of puberty. When you flood your body with synthetic testosterone, your system responds by converting some of that excess into estrogen through a process called aromatization. The result is the exact hormonal imbalance that drives breast tissue growth. This is why gynecomastia is so common among bodybuilders, even those who appear extremely lean and muscular.
Alcohol is another contributor, particularly with heavy or chronic use. Alcohol can suppress testosterone production and, when it damages the liver over time, impairs the organ’s ability to break down estrogen (more on that below). Marijuana has also been linked to gynecomastia, though the evidence is less definitive than for steroids or alcohol.
Even some topical products can play a role. Tea tree oil and lavender oil, found in certain shampoos, soaps, and lotions, contain compounds that mimic estrogen or interfere with testosterone. This has been documented particularly in younger boys exposed to these products regularly.
Liver, Kidney, and Thyroid Problems
Your liver is responsible for breaking down and clearing estrogen from your bloodstream. When liver disease, particularly cirrhosis, damages that function, estrogen accumulates while testosterone drops. Cirrhosis also increases the breakdown of testosterone and can cause the testes to produce less of it. The combination creates a strong hormonal push toward breast tissue growth, which is why gynecomastia is common in men with advanced liver disease.
Kidney failure creates a similar hormonal disruption. The kidneys play a role in clearing hormones and maintaining their balance, and when that system fails, testosterone levels often fall. Thyroid disorders, particularly an overactive thyroid, can also shift the estrogen-to-testosterone ratio enough to trigger gynecomastia.
If you have no obvious explanation for your gynecomastia, these underlying conditions are part of what a doctor would screen for. Breast tissue growth can sometimes be the first noticeable sign of an organ or hormone problem that hasn’t produced other symptoms yet.
Aging and Natural Testosterone Decline
Testosterone production gradually decreases as men age, typically starting in the mid-30s and continuing through later decades. Body fat also tends to increase with age, and fat tissue produces a small amount of estrogen. The combination of declining testosterone and rising estrogen makes gynecomastia increasingly common in older men, even those who are otherwise healthy. This is the second major peak in prevalence after puberty.
How Severity Is Classified
Doctors grade gynecomastia on a scale that helps determine whether treatment is appropriate:
- Grade I: A small, localized button of tissue concentrated around the areola. Often only noticeable by feel.
- Grade II: Moderate enlargement that extends beyond the areola, with edges that blend into the surrounding chest.
- Grade III: Moderate to significant enlargement beyond the areola with distinct edges and excess skin.
Grade I is the most common presentation, especially from puberty or mild hormonal shifts. Higher grades are more likely with prolonged hormonal imbalance, steroid use, or underlying disease, and they’re less likely to resolve without surgical treatment.
When Breast Changes Need Urgent Attention
Gynecomastia is almost always benign, but male breast cancer does exist and can initially feel similar: a lump under or near the nipple. A few features should prompt you to get checked sooner rather than later. A hard, fixed lump that doesn’t feel rubbery or mobile is more concerning than the typical springy disk of gynecomastia. Nipple discharge, especially if bloody, is a red flag. Skin changes like crusting, scaling, redness, or dimpling around the nipple warrant evaluation. Swelling that’s warm, red, and tender without an obvious cause also needs attention. These symptoms are rare in men, but they overlap with conditions including Paget disease of the nipple and inflammatory breast cancer, both of which are treatable when caught early.