Hormone therapy

Hormone therapy slows or stops cancers that use hormones to grow, mainly breast and prostate cancer.

Rosa: Hi, I'm Rosa. Some cancers use hormones to grow. Let me explain how hormone therapy slows them down, and how to handle the side effects.

Some cancers use the body's hormones as fuel. Many breast cancers grow in response to estrogen or progesterone. These are called hormone receptor-positive (HR-positive) breast cancers. Most prostate cancers grow in response to testosterone and related hormones, called androgens. Hormone therapy, also called endocrine therapy, blocks or lowers these hormones so the cancer cannot use them.

Think of hormones as a key and the cancer cell as a lock. Some hormone medicines lower the number of keys made in the body. Others block the lock so the key cannot fit. Either way, the signal that tells the cancer to grow is turned down.

For breast cancer, common medicines include tamoxifen and aromatase inhibitors such as anastrozole, letrozole, and exemestane. They are usually pills taken daily. People who have not gone through menopause may also get shots to pause the ovaries. After surgery for early breast cancer, hormone therapy often lasts 5 years, and sometimes up to 10. For advanced breast cancer, it is often combined with targeted drugs.

For prostate cancer, the main treatment is androgen deprivation therapy (ADT). This is usually a shot or implant given every 1 to 6 months, or a daily pill, that lowers testosterone. Surgery to remove the testicles is another option. Newer pills, such as abiraterone, enzalutamide, apalutamide, and darolutamide, block androgens further and are often added. Length of treatment depends on the stage and may be months, years, or ongoing.

Side effects come from lowering hormones. Hot flashes are common in both breast and prostate cancer treatment. Other effects can include tiredness, joint aches (common with aromatase inhibitors), mood changes, lower sex drive, vaginal dryness, erection problems, weight gain, and loss of muscle. Some medicines can weaken bones, so your team may check bone density and suggest calcium, vitamin D, exercise, or bone-strengthening medicine. Tamoxifen slightly raises the risk of blood clots and uterine cancer.

Call your care team right away for leg swelling, pain, or warmth in one leg, sudden shortness of breath or chest pain, unusual vaginal bleeding (especially after menopause), sudden weakness or trouble speaking, a fall with bone pain, or severe mood changes. If it feels very bad, call 911.

Stick with it

Hormone therapy works best when taken every day for the full time prescribed. If side effects make it hard, tell your team. There are often ways to help or other drugs to try.

Hot flashes

Dress in layers, keep cool, and limit alcohol, caffeine, and spicy food. Ask about medicines that can help. Check with your team before using herbal products, since some act like hormones.

Bones and heart

Weight-bearing exercise like walking helps protect bones and muscles. Ask about bone density testing. Keep up with blood pressure, cholesterol, and blood sugar checks.

Other medicines

Some medicines, including certain antidepressants, can interact with tamoxifen. Ask your pharmacist to review all your medicines and supplements.

Questions to ask

Is my cancer hormone-sensitive? How long will I take hormone therapy? What side effects are most likely? How will you protect my bones? What if I want to have children later?

Myth: Hormone therapy is the same as menopause hormone pills

Fact: Cancer hormone therapy does the opposite. It blocks or lowers hormones that feed the cancer, instead of adding hormones.

Myth: Hormone therapy is not real cancer treatment

Fact: For hormone-sensitive breast and prostate cancers, hormone therapy is one of the most important treatments. It lowers the chance of the cancer coming back or growing.

Last updated: 2026-10-27. Medically reviewed by Veli Bakalov, MD, medical oncologist (October 2026). General education from Step by Step, the patient portal of HemeOncBuddy.