Can TRT cause gynecomastia?
Yes, but it’s uncommon. Gynecomastia on TRT means growth of breast gland tissue in a man taking testosterone. Every testosterone label we checked warns that it may develop.
Breast tenderness or a sore nipple can happen with or without visible growth. Both are worth mentioning to your prescriber. Neither is the same as breast cancer, which is rare in men.
What matters most is knowing which changes can wait for your next visit and which need a doctor soon. This page covers both. For the full list of side effects, see our guide to TRT side effects.
What is gynecomastia?
It’s a benign, or non-cancer, growth of breast gland tissue in men. A review in Mayo Clinic Proceedings says it usually comes from more estrogen activity, less testosterone activity, or a medicine.
MedlinePlus describes how it often starts. It begins as a small lump beneath the nipple, which may be tender. It can happen on one side or both, and over time the lump may feel firmer and less sore.
It’s very common in men generally. A European guideline puts it at 32% to 65% of men, depending on age and how it’s defined. Most of those men never notice it.
It gets more common with age. The Mayo review reports gland growth without symptoms in up to 70% of men aged 50 to 69. Growth that causes symptoms is much rarer.
When doctors look for a cause in adult men, they find one in about half of cases, the European guideline says. That’s why a new breast change is worth reporting, even on TRT.
Is it breast tissue or chest fat?
Many men with a fuller chest have extra fat, not gland tissue. Doctors call that pseudogynecomastia. It’s the most common reason for breast growth, MedlinePlus says.
The difference is in the feel:
- Gland tissue usually forms a firm or rubbery disc right under the nipple.
- Fat makes the whole chest softer and larger, without that disc.
An exam is the only reliable way to tell. Guidelines say a clinician should confirm gland tissue and rule out a worrying lump. So don’t try to settle it yourself.
How common is gynecomastia on TRT?
Less common than forums suggest. The American Urological Association (AUA) says breast symptoms are an uncommon side effect of testosterone. It also says gynecomastia has been rarely reported in placebo-controlled trials.
Here is what labels and trials report.
| Source | What it reports |
|---|---|
| DEPO-Testosterone and Azmiro (cypionate injections) | Gynecomastia may develop and occasionally persists |
| Xyosted (enanthate auto-injector) | Gynecomastia may develop and may persist |
| AndroGel 1.62% (gel) | May develop and persist; breast pain among reports after approval |
| AndroGel 1% (gel), 180-day trial | Gynecomastia in 0% to 3% of men across three gel strengths |
| AndroGel 1% (gel), three-year study | Gynecomastia in 2.5% of 162 men |
| AUA review of three trials | Only a handful of new cases; some men’s existing gynecomastia improved |
Some websites say 10% to 25% of men on TRT get it. We couldn’t find a study behind that figure.
We also found no reliable rate for men on injections in everyday care. Trials are small and short, and labels can’t give real-world rates.
When does gynecomastia start on TRT?
We don’t know for sure. We found no study that tracked when breast symptoms begin in men on TRT.
The trials the AUA reviewed lasted from 16 weeks to six months, and the few cases appeared within that time. The AndroGel 1% study found cases over three years. So it can show up early or later on.
Track any change from the day you notice it. A date in your notes is more useful to your prescriber than a guess months later.
Why can testosterone cause breast growth?
Your body turns some testosterone into estradiol, a form of estrogen. An enzyme called aromatase does this. The AUA says it’s not unusual for estradiol to rise on testosterone therapy.
Aromatase is found in many tissues, including fat. A 2025 review says this likely explains why men with more body fat convert more testosterone to estradiol.
Breast tissue responds to the balance between estrogen and testosterone. A 2026 Italian guideline says the trigger is often a shift in that balance, not just a high estrogen number.
Does the type of TRT matter?
It may affect estradiol. A clinic review of 178 men found estradiol rose on gels, injections and pellets. The rise was larger with injections and gels, though the injection group was younger.
A small 1987 study of 11 men measured estradiol after a cypionate shot. It roughly tripled in the first week, then fell back by about two weeks.
We found no study showing that one form causes more gynecomastia than another. If you notice symptoms soon after each shot, write it down for your prescriber.
Tenderness can wait for your next visit; a hard, fixed lump shouldn’t.
Should you get your estradiol checked?
It’s a question for your prescriber. The guidelines aren’t simple here.
- Before starting TRT: the AUA says estradiol should be measured in men who already have breast symptoms.
- During TRT: for symptoms that start on treatment, the AUA suggests a period of watching, because symptoms sometimes fade. One part of its guideline calls the estradiol test optional in that case.
- Routine checks: the Endocrine Society’s monitoring plan names symptoms, side effects, testosterone, hematocrit and prostate checks. It doesn’t name estradiol.
There is no single estradiol number that causes breast growth. The 2025 review says the best testosterone-to-estradiol ratio hasn’t been worked out. Your symptoms matter as much as the lab value.
Our estradiol guide explains the test and how results are read. If you do get it checked, our blood test timing planner helps you time draws, so results are easier to compare.
Does gynecomastia from TRT go away?
Sometimes. The AUA says breast symptoms that start on treatment sometimes fade. In one trial it reviewed, some men’s existing gynecomastia improved or went away during treatment.
But labels also warn that it can persist. MedlinePlus says breast growth that has been there a long time is less likely to go away, even with treatment.
The Italian guideline describes two phases. Gynecomastia under a year old is often still active, while after a year it tends to settle into firmer tissue.
That firmer tissue is harder to reverse. It’s one more reason to mention changes early.
Is a lump under the nipple a sign of breast cancer?
Usually not, but any new lump deserves a check. Breast cancer in men is rare.
The American Cancer Society says fewer than 1% of US breast cancers happen in men. A man’s lifetime risk is about 1 in 755, and most men are diagnosed in their 60s or 70s.
Gynecomastia itself is not a precancer, the European guideline says. Still, the AUA notes that any male breast growth should be checked with cancer in mind.
The NCI says screening mammograms aren’t usually advised for men. So checks happen when you or your doctor notice a change, which is why reporting one matters.
Testosterone labels say not to use testosterone if you have breast cancer. The Endocrine Society also advises against starting it then. We found no clear evidence on whether TRT changes breast cancer risk in men with low testosterone.
Which breast changes need a doctor soon?
The National Cancer Institute (NCI) says most breast changes in men are benign but should still be checked. See a doctor soon, not at your next routine visit, if you notice:
- A hard or firm lump, especially one that feels stuck in place. The American Cancer Society says cancer lumps are usually, but not always, firm and painless.
- A lump off to one side of the nipple, or growth on one side only.
- Fluid from the nipple, clear or bloody, or a nipple that turns inward.
- Skin changes: dimpling like orange peel, redness, scaling or an open sore.
- Swollen lumps under the arm or near the collarbone.
Don’t take tenderness as a sign that a lump is harmless. The Italian guideline lists a hard, tender lump beyond the nipple area among warning signs.
Call your prescriber about new breast swelling, pain or a rubbery lump under the nipple. Testosterone Medication Guides ask you to report enlarged or painful breasts.
What will your doctor check?
Usually, a history and an exam. The Italian guideline says most gynecomastia can be diagnosed by exam alone. Expect questions about when it started, your medicines, alcohol and other substances.
Depending on what they find, a clinician may order:
- Blood tests: testosterone, estradiol, SHBG, LH and FSH, thyroid, prolactin, and liver and kidney tests. These come from the European guideline’s list.
- An exam of the testes, sometimes with an ultrasound.
- Breast imaging if the exam is unclear: ultrasound for men under 25, or a mammogram for men 25 and older.
- A needle biopsy, a small tissue sample, if a lump looks suspicious.
What else can cause breast growth in men?
TRT isn’t always the reason. MedlinePlus lists many other causes:
- Body fat, the most common cause of a larger chest.
- Liver or kidney disease, and thyroid problems.
- Alcohol, marijuana and anabolic steroids.
- Some medicines, including one used for hair loss.
Tell your prescriber about everything you take, including supplements and anything bought online. The European guideline says doctors look for these causes first, then watch and wait once they’re dealt with.
Your doctor will look at all of these before blaming testosterone. Finding another cause can change what happens next.
What can be done about gynecomastia on TRT?
That’s a decision for you and your prescriber. Guidelines for gynecomastia in general often start with watchful waiting, especially for new cases. Your prescriber may also look at your treatment or your labs.
For long-standing or distressing cases, guidelines describe medicines and surgery as options a specialist may discuss. They don’t agree on which medicines help. Don’t buy anything online to treat it yourself.
And don’t stop TRT on your own. Your prescriber can weigh your symptoms against the reasons you started.
What should you note and ask your prescriber?
A short record helps your prescriber judge what’s going on.
Note:
- Which side: left, right or both.
- When it started, compared with starting TRT or any change.
- Whether it’s tender, swollen or a lump you can feel.
- Whether it changes in the days after each shot.
- Any new medicine, supplement or change in your weight.
- How much alcohol you drink, and whether you use marijuana or other substances.
Ask:
- Is this gland tissue or fat?
- Do I need any blood tests or imaging?
- Is there anything about my treatment we should look at?
- Should I see a specialist?
- What change would mean I should come back sooner?
Our guide to preparing for your TRT appointment has more questions to bring.