Some cancer treatments lower the amount of sex hormones in the body. The sex hormones are oestrogen and progesterone in women and testosterone in men.

There is some evidence to suggest that hormone treatments for breast cancer called aromatase inhibitors may cause heart problems in women.

Hormone therapy may increase heart problems

Research suggests that women who take hormone therapies called aromatase inhibitors may be at a slightly higher risk of heart problems.

The group of aromatase inhibitors includes the drugs:

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

Research into hormone therapies and heart problems

It is not certain why there is a higher risk of heart problems. Researchers think it may be because the hormone therapy increases the amount of cholesterol in the blood. This is a rare but serious side effect and is especially important for women who already have heart problems.

Some research shows that the risk of heart problems is higher in women who take an aromatase inhibitor for 5 years. The risk might be lower if you switch from one type of hormone treatment to another.

For example, researchers found that women who took the hormone therapy tamoxifen for 2 or 3 years and then switched to an aromatase inhibitor for a few years didn't have a higher risk of heart problems.

Researchers are also looking into the possibility that tamoxifen may protect against heart problems. It can lower the level of fat lipids in the blood. High levels of fat can lead to heart disease. But there is no research yet to say that tamoxifen does protect from heart disease. 

Balancing the benefits of treatments against side effects

All treatments have side effects. Doctors balance the risk of side effects against the benefit of the treatment in treating cancer.

Tamoxifen can very occasionally cause serious side effects, including blood clots and womb cancer. Aromatase inhibitors cause a number of side effects, including bone weakening (osteoporosis).

Starting on one type of hormone therapy and then switching to another might reduce the side effects of both. We need more research to confirm how best to use hormone treatments for breast cancer.

It is important to remember that these hormone treatments reduce the risk of the cancer coming back. The risk of the cancer coming back is greater than the risk of heart problems for most people.

If you already have heart problems or have a high cholesterol level and are worried about this you can talk to your cancer specialist.

Tips to help lower your risk of heart disease

• Maintain a healthy weight
• Eat a healthy well balanced diet
• Be physically active, exercise regularly