Gynaecomastia is an increase in breast gland tissue in boys or men, caused by an imbalance between estrogen and testosterone. It is not the same as having excess chest fat. The condition involves actual glandular tissue growing beneath and around the nipple, which can make the chest appear similar to female breasts.
How Hormones Drive Breast Growth in Men
Every male body produces small amounts of estrogen alongside testosterone. Normally, testosterone keeps estrogen’s effects in check. Gynaecomastia develops when that balance tips, either because estrogen levels rise, testosterone levels fall, or both happen at once.
When estrogen activity outweighs androgen activity at the breast tissue level, it triggers growth of the milk ducts and surrounding glandular tissue. A protein in the blood called sex hormone-binding globulin also plays a role: it binds to testosterone and makes it unavailable, effectively shifting the ratio further toward estrogen. This is why conditions that raise this binding protein, such as an overactive thyroid or chronic liver disease, can trigger breast growth even when estrogen levels themselves aren’t dramatically elevated.
Fat tissue contains an enzyme that converts androgens into estrogen. This is one reason gynaecomastia is more common in men who carry extra body weight. The more fat tissue present, the more conversion takes place, pushing the hormonal balance toward estrogen.
Three Life Stages Where It’s Common
Gynaecomastia clusters around three predictable windows. In newborns, maternal estrogen crosses the placenta and can cause temporary breast swelling that resolves on its own within weeks. During puberty, hormone levels fluctuate dramatically as the body matures, and breast tissue growth is extremely common in teenage boys. In most adolescents, the tissue shrinks without treatment as hormone levels stabilize, typically within six months to two years.
The third peak occurs after age 60. Testosterone production gradually declines with aging, while total body fat tends to increase. That combination creates more estrogen conversion in fat tissue and less testosterone to counterbalance it. The result is a slow shift in the hormonal ratio that can produce noticeable breast tissue over time.
Medical Conditions That Cause It
Beyond the normal life stage peaks, several health conditions can trigger gynaecomastia by disrupting hormones. An overactive thyroid increases the binding protein that ties up free testosterone, leaving estrogen relatively unopposed. Chronic liver disease, particularly cirrhosis, impairs the liver’s ability to break down estrogen and also raises binding protein levels. Kidney failure affects hormone clearance in a similar way.
Certain tumors can also be responsible. Tumors in the testicles (Leydig cell or Sertoli cell tumors) may produce estrogen directly. Adrenal tumors can release hormone precursors that get converted to estrogen elsewhere in the body. Rarer tumors in the lungs, stomach, or liver sometimes produce a hormone called hCG that stimulates estrogen production. These causes are uncommon but worth investigating when gynaecomastia appears suddenly or progresses quickly in an adult man.
Medications That Trigger Breast Growth
Drug-induced gynaecomastia is one of the most frequent causes. More than 50 individual medications have been linked to breast tissue growth, and the list spans a surprising range of drug types.
- Spironolactone (a blood pressure and heart failure drug) is one of the most well-documented culprits. In one study, all 14 men receiving it developed gynaecomastia.
- Cimetidine, an older heartburn medication, caused breast soreness and swelling in about one in five men taking it for several months.
- Finasteride, used for hair loss and prostate enlargement, appears repeatedly in case reports.
- Certain HIV medications, including efavirenz and antiretroviral combination therapy, are associated with breast tissue changes.
- Some calcium channel blockers (amlodipine, nifedipine, verapamil, diltiazem), statins, antifungals like ketoconazole, and antidepressants like fluoxetine and venlafaxine have also been implicated.
If you notice breast tissue growth after starting a new medication, the connection is worth raising with whoever prescribed it. In many cases, switching to an alternative resolves the problem.
Gynaecomastia vs. Chest Fat
Not all enlarged male chests involve glandular tissue. Pseudogynaecomastia is the medical term for chest enlargement caused purely by fat deposits, with no glandular growth underneath. The distinction matters because the causes and treatments differ.
During a physical exam, a doctor can tell the difference with a simple technique. While you lie on your back with your hands behind your head, the examiner places a thumb and forefinger on either side of the breast and slowly brings them together. In true gynaecomastia, they’ll feel a firm, rubbery disc of tissue centered directly behind the nipple. In pseudogynaecomastia, there’s no firm disc at all: the fingers meet no resistance until they reach the nipple itself. Ultrasound or mammography is sometimes used when the physical findings are unclear or when there’s concern about a lump that doesn’t feel typical.
Grading the Severity
Doctors commonly use a four-tier system first described in 1973 to classify how advanced gynaecomastia is:
- Grade I: Small enlargement with no excess skin
- Grade IIa: Moderate enlargement with no excess skin
- Grade IIb: Moderate enlargement with some excess skin
- Grade III: Marked enlargement with significant excess skin, closely resembling a female breast
This classification helps guide treatment decisions. Lower grades respond better to medication or minor procedures, while Grade III typically requires more extensive surgery to address both the tissue and the stretched skin.
Treatment Options
For pubertal gynaecomastia, the first approach is usually watchful waiting, since the tissue resolves on its own in most teenage boys. When it doesn’t, or when it causes significant discomfort or distress, medication can help. Tamoxifen, which blocks estrogen’s effect on breast tissue, has strong evidence behind it. Given at 20 mg daily for three to six months, it produced significant regression in roughly 90% of teenage boys in one study, shrinking breast tissue by nearly half. A related medication, raloxifene, showed slightly better results in the same research.
When gynaecomastia is caused by a specific medication, stopping or switching that drug often leads to improvement. If an underlying condition like thyroid disease or liver dysfunction is responsible, treating that condition addresses the root cause.
Surgery becomes the main option for long-standing gynaecomastia that hasn’t responded to other approaches, or when there’s significant excess skin. For lower grades, the procedure typically involves removing the glandular tissue through a small incision around the areola, sometimes combined with liposuction to remove surrounding fat. Higher grades may require skin removal as well, which leaves more visible scarring but produces a flatter chest contour. Recovery generally takes a few weeks before you can return to normal activity, with full results visible after swelling settles over several months.
What It Feels Like
Gynaecomastia often starts as tenderness or sensitivity around one or both nipples. You might notice a small, firm lump directly behind the nipple that feels distinctly different from the surrounding tissue. The enlargement can be one-sided or affect both sides, and it’s common for one side to be slightly larger than the other. Some men experience ongoing soreness, while others have tissue growth without any pain at all. The psychological impact is often more significant than the physical symptoms, particularly for adolescents, with many reporting self-consciousness about their appearance that affects clothing choices, physical activity, and social confidence.