Hormone Therapy

What is hormone therapy?

Hormone therapy (HT), also called menopausal hormone therapy, is a treatment for women who are going through or have gone through menopause. The female hormone estrogen is the most common type of hormone therapy. Because taking estrogen alone may increase the risk of uterine cancer, it is usually combined with another type of hormone called a progestogen.¹ Estrogen alone is only given to women who have had a hysterectomy (had their uterus surgically removed).²

See also: Age & Menopause

What is hormone therapy used for?

Hormone therapy is used to treat menopausal symptoms such as hot flashes, night sweats, sleep disturbances, and vaginal dryness.

Hormone therapy has also been investigated as a way to prevent or treat many diseases that become common after menopause—from heart disease, stroke, and cancer to Alzheimer's disease and osteoporosis—but results have generally been disappointing so far.

What are the different kinds of hormone therapy?

There are three main types of hormone therapy:

• Estrogen-only therapy (ET)
• Progestogen-only therapy
• Combined estrogen-progestogen therapy (EPT)

There are many variations on these main themes: hormone therapies come in different combinations of estrogens and progestogens, with different dosing strengths and schedules. It is generally recommended that you use the lowest dose that controls your symptoms.

Hormone therapy can be applied in many ways. It is usually given as a pill, but can also be given as an injection, or absorbed through the skin as a patch, gel, cream, or spray, or as a vaginal cream, ring, or tablet. For a list of the different hormone therapy formulations available in the US and Canada, visit http://www.menopause.org/edumaterials/htcharts.pdf.

Click here to learn about custom-compounded and bioidentical hormones.

How do my body's natural hormones affect my risk of stroke?

Women tend to develop stroke and heart disease later in life than men. This delay is thought to be largely due to the protective effects of estrogen. Estrogen alters the levels of cholesterol and fat in your blood,² changes the way your blood forms clots,³ affects how well your blood flows though the body and how the blood vessels respond,^{4, 5} and has an impact on many factors related to the buildup of fatty plaque in the arteries. All of these processes influence the development of heart disease and stroke.⁶

When a woman goes through menopause, her body stops producing estrogen and these protective effects are lost. After menopause a woman's risk of heart disease and stroke begins to increase. It was therefore thought that replacing the lost estrogen might help prevent heart and blood vessel disease.

Does hormone therapy increase my risk of having a stroke?

Yes. Hormone therapy, either estrogen alone or combined with progestin, increases your risk of stroke and does not prevent you from having a heart attack or dying of heart disease.^{7, 8} In the past, some doctors prescribed hormone therapy in an attempt to lower the risk of heart and blood vessel disease, but current guidelines state that hormone therapy should not be used to treat or prevent heart disease or stroke in women.⁹

Early studies that compared women who chose to take hormone therapy with those who didn't showed that hormone therapy users had a lower risk of heart disease and the same risk of stroke, but that they were likely to have less severe strokes.^{1, 10, 11, 12} However, when more tightly controlled experiments randomly assigned women to hormone therapy or a dummy pill, the results were not positive.

The Women's Health Initiative study of more than 16,000 healthy postmenopausal women found that a combination of estrogen and progestin provided no protection from heart attack, stroke or heart disease.⁷ In fact, hormone therapy users had a slightly higher risk of heart disease, stroke, and blood clots.¹³ The trial was stopped early because women taking hormone therapy also began to show an increased risk of breast cancer. The Women's Health Initiative also found that estrogen alone increased the risk of stroke and blood clots and had no effect on the risk of heart disease or breast cancer.¹⁴ Overall, researchers decided that while the risk of harm is small from using hormone therapy to prevent heart disease and stroke, it still outweighs any potential benefits.

The increases in stroke risk when using hormone therapy to treat menopausal symptoms is relatively small. Over 1 year, if 10,000 healthy women were to take combination hormone therapy, 8 more women would suffer a stroke compared with a group of 10,000 women not taking hormone therapy.¹³ In women with a hysterectomy who are taking estrogen-only hormone therapy, there would be 12 additional strokes per 10,000 women treated. See also: What are the Risks and Benefits of Hormone Therapy?

Most studies of hormone therapy have only looked at one type of estrogen-plus-progesterone pill, called Prempro, and one type of estrogen alone pill, called Premarin. It is not known whether other forms of hormone therapy have the same effects. Some research has shown that when hormones are imbedded in a patch and absorbed through the skin, they affect the body differently.¹³

Do the stroke risks of hormone therapy change with age?

When women of all ages are looked at together, using hormone therapy increases the risk of stroke and heart disease. Results from the Women's Health Initiative study of hormone therapy found that younger women taking hormone therapy within 5 years of menopause may not be at increased risk for heart disease, and may actually have a slightly lower risk.¹⁵ The effects of younger age on stroke were smaller, with an increased stroke risk regardless of years since menopause. However, while stroke risk did not decrease in women of any age taking hormones, in women aged 50 to 59 there was no significant increase in risk with therapy.¹⁵

For now, hormone therapy should not be taken to prevent heart disease or stroke even among very young postmenopausal women. However, the results of studies like the Women's Health Initiative should reassure younger women who want to take HT for menopausal symptoms that they need not be scared off by the possible stroke risks.¹⁶

Can I take hormones for menopausal symptoms if I have a history of stroke?

No. If you have had a stroke or blood clots in the past, or have been diagnosed with heart disease, you should not take hormone therapy.¹⁷ A study of women who had already had a stroke or transient ischemic attack (TIA) found that estrogen-only hormone therapy did not decrease the risk of having another stroke, and actually doubled the risk of having a recurrent stroke in the first 6 months of therapy.¹⁸ Among women who had another stroke, those who were taking estrogen therapy were 3 times as likely to die; those who survived had worse mental and functional disabilities. Combination hormone therapy increases the risk of stroke and blood clots and increases the risk of heart attack in the first year of therapy.^19-23

What alternatives to hormone therapy are being studied?

Currently, researchers are looking into a group of drugs called Selective Estrogen-Receptor Modulators (SERMs), which have also been called "designer estrogens." They are compounds that have beneficial effects on bone density like estrogen, but without estrogen's negative effects on the breast or lining of the uterus. The hope is that these new compounds will provide the benefits of replacement estrogen without the negative side effects, such as stroke, heart problems, and cancer. So far, most studies of SERMs have found that although they have better risk profiles for heart disease, like hormone therapy they increase the risk of stroke and blood clots.

The most studied of the four FDA-approved SERMs is raloxifene (Evista), used to prevent and treat postmenopausal osteoporosis (thinning of the bones) and to prevent breast cancer in women at high risk. In the RUTH trial, over 10,000 women with heart disease or multiple risk factors received raloxifene or a dummy pill once a day for more than 5 years. Raloxifene cut the risk of breast cancer and spine fractures, and did not increase the risk of heart attack, hospitalization for heart disease, or dying of heart disease. However, women taking raloxifene had a slightly higher risk of dying of a stroke or having blood clots in the leg veins, which can move to other parts of the body.²⁴

Current guidelines state that, like hormone therapy, SERMs should not be used for the prevention or treatment of heart disease or stroke in women.⁹

See also:

• For a summary of the overall benefits and risks of hormone therapy, click here
• For information on how to decide whether or not to take hormone therapy and the alternatives to hormone therapy, click here
• Click here for information on the relationship between hormone therapy and heart disease risk

For More Information

National Heart Lung and Blood Institute Facts about menopausal hormone therapy
www.nhlbi.nih.gov/health/women/

FDA Menopause & Hormones Information
www.fda.gov/womens/menopause/

National Women's Health Information Center – Menopause & Menopause Treatments
http://www.womenshealth.gov/faq/menopause-treatment.cfm

List of Hormone Products for Postmenopausal Use in the United States and Canada
The North American Menopause Society
www.menopause.org/edumaterials/htcharts.pdf

References

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