What are the benefits and risks of long-term hormone therapy?

Hormone therapy can help ease symptoms of menopause. But it is associated with a lot of serious risks if used over the long term. Although the treatment lowers the risk of bone fractures, it increases the risk of cardiovascular disease (heart and blood vessel problems) and breast cancer.

Women’s hormone levels change during the time leading up to menopause (known as perimenopause). This can lead to hot flashes, sweats and mood swings. Some women have such severe symptoms that they start looking for treatments. One treatment option is hormone therapy with estrogen, or with a combination of estrogen and progestin. Combination drugs are generally used because estrogen can lead to growths in the lining of the womb when used alone. So estrogen-only medications are only suitable for women who have had a hysterectomy (surgery to remove their womb).

In the past it was thought that taking hormones for a long time after menopause can protect women from serious diseases. But this assumption turned out to be wrong. On the contrary: It is now clear that this treatment actually increases the risk of certain serious diseases. These include:

Strokes
Heart attacks
Blood clots in the legs or in the lungs (thromboembolism)
Breast cancer

Pros and cons of hormone therapy

A summary of studies has shown that estrogen therapy and treatment with a combination of estrogen and progestin both have a lot of disadvantages – the longer the treatment lasts, the more disadvantages.

The following tables show how common certain medical conditions are in women who have long-term hormone therapy after menopause. The data was mainly taken from a large U.S. study called the "Women's Health Initiative Study" (see below).

Advantages of hormone therapy

The research suggests that long-term hormone therapy can prevent bone fractures. Some analyses of the studies also suggest that hormone therapy could lower the risk of bowel cancer somewhat.

Regarding bone fractures, the following advantage was found after eight years: Bone fractures occurred in

126 out of 1,000 women who had treatment with estrogen and progestin, and in
154 out of 1,000 women who didn't have hormone therapy (were given a placebo).

So the treatment prevents bone fractures in 28 out of 1,000 women.

Disadvantages of hormone therapy

The risk of various medical problems already increased after one year, and then continued to increase after that. The following disadvantages were found in women who had treatment with estrogen and progestin:

**Table**: Frequency of thromboembolism, stroke and breast cancer – with and without estrogen and progestin treatment.
Health problem and duration of treatment	Frequency when taking estrogen and progestin	Frequency without hormone therapy (placebo)	Disadvantage in
Thromboembolism8 years	25 out of 1,000 women	15 out of 1,000 women	10 out of 1,000 women
Stroke8 years	19 out of 1,000 women	14 out of 1,000 women	5 out of 1,000 women
Breast cancer8 years	33 out of 1,000 women	26 out of 1,000 women	7 out of 1,000 women

The risk of heart attacks might increase a little too. If women take a combination of estrogen and progestin for longer than five years, their risk of breast cancer will probably stay higher even after they stop hormone therapy. Also, one analysis showed that women who have long-term hormone therapy are more likely to develop dementia.

Women who only took estrogen didn't have a higher risk of breast cancer and heart attacks. They had a similar risk of stroke and thromboembolism as women who took a combination of estrogen and progestin did:

**Table**: Frequency of stroke and thromboembolism – with and without estrogen therapy
Health problem and duration of treatment	Frequency when taking estrogen	Frequency without hormone therapy (placebo)	Disadvantage in
Stroke7 years	32 out of 1,000 women	24 out of 1,000 women	8 out of 1,000 women
Thromboembolism7 years	21 out of 1,000 women	16 out of 1,000 women	5 out of 1,000 women

Weighing the pros and cons

Based on current research findings, it's not advisable to take hormones as a preventive measure or over a long period of time.
If you have severe menopause-related problems, it's a good idea to carefully weigh the pros and cons of hormone therapy together with your doctor.
If you decide to use hormones, the treatment should be as short as possible, using the lowest dose possible.

Marjoribanks J, Farquhar C, Roberts H, Lethaby A, Lee J. Long-term hormone therapy for perimenopausal and postmenopausal women. Cochrane Database Syst Rev 2017; (1): CD004143.

IQWiG health information is written with the aim of helping people understand the advantages and disadvantages of the main treatment options and health care services.

Because IQWiG is a German institute, some of the information provided here is specific to the German health care system. The suitability of any of the described options in an individual case can be determined by talking to a doctor. informedhealth.org can provide support for talks with doctors and other medical professionals, but cannot replace them. We do not offer individual consultations.

Our information is based on the results of good-quality studies. It is written by a team of health care professionals, scientists and editors, and reviewed by external experts. You can find a detailed description of how our health information is produced and updated in our methods.

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