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About hormone therapy

Find out what hormone therapy is, when you might have it, and the possible side effects.

What hormones are

Hormones are made naturally in the body. They control the growth and activity of normal cells.

Before the menopause, the ovaries produce the hormones oestrogen and progesterone. After the menopause, oestrogen is made in body fat.

These hormones can stimulate the growth of some breast cancer cells.

Oestrogen diagram

How hormone therapy works

Hormone treatments lower the levels of oestrogen or progesterone in the body, or block their effects.

Hormone therapy is only likely to work if the breast cancer cells have oestrogen receptors (ER). Your doctor checks your cancer cells for these receptors when you are diagnosed. 

Around 7 out of 10 breast cancers (70%) have oestrogen receptors, They are called oestrogen receptor positive cancer or ER positive cancer.

When you have hormone therapy

After surgery

It is most common to have hormone therapy after surgery for breast cancer. This is called adjuvant treatment.

If you are also having chemotherapy after surgery, you start the hormone therapy once chemotherapy finishes. If you are having radiotherapy after surgery, you can have hormone therapy at the same time or start it afterwards.

The aim of treatment after surgery is to lower the risk of the cancer coming back.

You have hormone therapy for 5 years or more. But exactly how long depends on the type of drug you have and your individual situation.

Before surgery

Treatment before surgery is called neo adjuvant therapy. If your cancer has oestrogen receptors, you might have hormone therapy to shrink a large or locally advanced breast cancer.

This might mean that you can have a smaller operation. For example, you might be able to have just the tumour removed (a lumpectomy) instead of the whole breast (mastectomy).

Your doctor will monitor the cancer during the time you have the hormone therapy to check that it is getting smaller.

If you can’t have surgery

Surgery is the main treatment for breast cancer but some women have health problems that mean they can’t have surgery. Some women choose not to have surgery.

In this case, if your breast cancer is oestrogen receptor positive, your doctor might recommend hormone therapy. This treatment won't get rid of the cancer but can stop it growing or shrink it.

The treatment can often control the cancer for more than 18 months or 2 years. If it starts growing again, your doctor might change you to a different type of hormone treatment.

Advanced cancer

Hormone therapy is also used to treat advanced breast cancer.

Types of hormone therapy

There are different types of hormone therapy. These include:


Tamoxifen is one of the most commonly used hormone therapies for breast cancer. Women who are still having periods (are premenopausal) and women who have had their menopause (post menopausal) can take tamoxifen.

Tamoxifen works by blocking the oestrogen receptors. It stops oestrogen from telling the cancer cells to grow.

Aromatase inhibitors (AIs)

Aromatase inhibitors are the main hormone treatment used for post menopausal women. They work by stopping oestrogen being made in body fat after the menopause.

AIs include:

  • anastrozole (Arimidex)
  • letrozole (Femara)
  • exemestane (Aromasin)

Stopping the ovaries working (ovarian ablation)

In premenopausal women, doctors might use a type of hormone treatment to stop the ovaries from producing oestrogen. Or they might remove the ovaries.

The type of hormone treatment you have depends on different factors, including:

  • whether or not you have had the menopause
  • the risk of your cancer coming back
  • the side effects of the drug

Hormone therapy after the menopause

You are most likely to have anastrozole or letrozole for 5 years. Or you might have one of these drugs for 2 years followed by tamoxifen for 3 years.

If you can't have an aromatase inhibitor, you'll have tamoxifen for 5 years.

Other options might include:

  • taking tamoxifen for 2 to 3 years and then switching to an aromatase inhibitor for a total of 5 years
  • taking tamoxifen for 5 years and then letrozole for a further 5 years

Your doctor will think about your general health and possible side effects of the drugs when deciding which hormone treatment will be best for you.

Hormone therapy before the menopause

You are likely to have tamoxifen for 5 years. Your doctor might recommend that you take it for another 5 years after this. They will weigh up the benefit of taking the drug for longer with other factors, such as any side effects you have and whether you want to have children.

If you can't have tamoxifen due to the side effects, you might have an aromatase inhibitor with drug treatment to stop your ovaries working. Or your doctor might recommend surgery to remove your ovaries.

Your doctor might also suggest having treatment to stop your ovaries working if they offer you chemotherapy after surgery but you decide not to have it.

If you have your menopause while on tamoxifen

You might switch to an aromatase inhibitor (AI), such as letrozole, if you have your menopause while taking tamoxifen treatment.

Drug treatment to stop your ovaries working

The drug most commonly used is goserelin (Zoladex). Or you may have another drug called leuprorelin (Prostap). You have one of these as an injection once a month. They work by blocking a hormone produced in the pituitary gland that stimulates your ovaries to make and release oestrogen.

They stop your ovaries working, so you won't have periods or release eggs while you are having the injections.

You are likely to have menopausal symptoms, such as hot flushes and mood changes while you are having either of these drugs.

When you stop taking the drug, your ovaries should start working again. But, if you are close to the age at which your menopause would naturally start, your periods might not start again.

Surgery to remove your ovaries

You might choose to have an operation to remove your ovaries instead of having drug treatment to stop them working. You have this operation as keyhole surgery. It is called laparoscopic oophorectomy and you have it under general anaesthetic. You usually stay in hospital overnight.

The surgeon makes a number of small cuts into your tummy (abdomen). They put a long bendy tube called a laparoscope into one of the cuts. The laparoscope connects to a video screen.

The surgeon puts small instruments through the other cuts to carry out the operation and remove the ovaries. They close the cuts with stitches and cover them with small dressings.

Removing your ovaries causes a sudden menopause. The symptoms include hot flushes, sweating and mood swings. 

Early menopause

All the treatments that stop your ovaries working give you an early menopause but this might be temporary with goserelin. Some women find this very difficult to deal with. You are likely to have menopausal symptoms that start very suddenly.

How you have hormone therapy

Tamoxifen or aromatase inhibitors

You take tamoxifen or aromatase inhibitors as a tablet once a day, usually for at least 5 years. Your doctor will tell you exactly how long to take your treatment for.


Goserelin (Zoladex) is an injection just under the skin of your tummy (abdomen). You have it once every 4 weeks.

Before starting hormone therapy

If you are starting treatment with an aromastase inhibitor or goserelin, you have a DEXA scan first to check your bone strength (bone density). This is because these drugs can cause bone thinning (osteoporosis). You might have calcium and vitamin D supplements to help reduce the effect on your bones.

Side effects

Some side effects are common to all hormone therapies. Some effects vary from drug to drug.

The main side effects of hormone therapy include:

  • hot flushes and sweating
  • changes to your periods if you are pre menopausal
  • less interest in sex
  • vaginal dryness or discharge
  • feeling sick
  • painful joints
  • mood changes
  • tiredness

Many women find that the side effects are often worse at the start of treatment. They usually settle down after a few weeks or months.

Tell your doctor or nurse if you have any side effects. They may be able to help reduce them.

Information and help

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