Breast swelling and tenderness

Hormone therapy may cause swelling (gynaecomastia) and tenderness in the chest area. This is caused when levels of oestrogen and testosterone change because of hormone therapy. The amount of swelling can vary from a small amount of swelling to noticeably larger breasts. Tenderness can affect one or both sides of the chest and can range from mild sensitivity to long-lasting pain.

For men taking anti-androgen tablets (such as bicalutamide) on their own, breast swelling and tenderness is the most common side effect. If you take oestrogen tablets, you may also get breast swelling. It’s less common if you are having an LHRH agonist or GnRH antagonist, have had surgery to remove the testicles, or are having more than one type of hormone therapy at the same time (combined hormone therapy). Most men taking a high dose of the anti-androgen bicalutamide for more than six months will get breast swelling.

If you put on weight while you’re on hormone therapy, this can also lead to larger breasts.

What can help?

Breast swelling and tenderness can make men feel uncomfortable or embarrassed about their bodies. If you’ve put on weight while having hormone therapy, a balanced diet and regular exercise may help you lose weight, including from your chest area.

There are also treatments available that can help prevent or reduce breast swelling and tenderness, including the following.

Tamoxifen tablets

These can be taken once a week to help prevent or treat breast swelling and tenderness in men taking anti-androgen tablets. They work by stopping the hormone oestrogen from reaching the breast tissue. Tamoxifen may be an option if radiotherapy hasn’t helped to prevent breast swelling. You might not be able to have tamoxifen if you're taking oestrogen tablets, because it may stop the oestrogens from working properly. We don’t know how tamoxifen affects other hormone treatments in the long term. If you have hot flushes, some men find that taking tamoxifen tablets can make these worse.

Surgery

Surgery may also be used to treat breast swelling by removing painful or swollen areas of the breast. This treatment carries a risk of damage to the nipple and a loss of feeling. It’s usually only offered if other treatments haven't helped to reduce the breast swelling. It’s not available at all hospitals, so talk to your doctor or nurse about whether surgery is an option for you.

Radiotherapy

If you are about to start long-term anti-androgens, your doctor may suggest treating the breast area with a single low dose of radiotherapy, but this isn’t common. Ask your doctor about if this is an option for you.

References and reviewers

Updated: April 2025 | Due for Review: April 2028