Hormone replacement therapy refers to providing a woman who has gone through menopause with hormones that her body has stopped producing. Menopause, also referred to as the "change of life," occurs when a woman's ovaries stop producing the hormones estrogen and progesterone. When menopause occurs, menstruation stops and a woman is no longer able to conceive. The average age of menopause is about 50 years old.

Menopause can also occur when a woman has an operation in which her ovaries are removed (oophorectomy). This type of menopause is known as surgical menopause because it has occurred due to a surgical procedure.

Why is menopause important?

U.S. women now live one-third of their lives after menopause. Women are living longer. The average life expectancy for a U.S. woman is about 76 years. This is important because scientists are discovering many physical changes that occur after menopause that influence a woman's risk of disease, including bone loss, coronary heart disease and cancer.

What are the benefits of hormone replacement therapy?

One immediate benefit of hormone replacement therapy is the relief of uncomfortable symptoms that may occur with menopause, such as "hot flashes" (a wave of heat and sweating), night sweats and painful intercourse. Hormones also help alleviate other menopausal symptoms, such as changes in urination, irritability and depression.

Osteoporosis - Another benefit of therapy is prevention of bone loss. Bone loss speeds up after a woman's body stops producing estrogen on its own. This bone loss, which results in fragile, brittle bones that break easily, is called osteoporosis.

Are there other beneflts to hormone replacement therapy?

Coronary heart disease - In addition to the relief of menopausal discomforts and the prevention of osteoporosis, hormones appear to reduce a woman's risk of serious coronary heart disease, including heart attack. After menopause a woman's risk of having a heart attack rises quickly, approaching the same risk as for a man. In addition, the first heart attack is more likely to be fatal among women than among men. A woman who takes estrogen has about a 50% less chance of death from coronary heart disease than a woman not taking estrogen.

For women taking both estrogen and progestin, the exact amount of the benefit is not clear. It appears that the combination of both hormones can still lower a woman's risk of coronary heart disease, but it is not certain if the benefit will be as great as 50%.

What are the risks?

The risks depend on the type of treatment prescribed, whether the woman has a uterus, and how long hormones are taken. With short-term therapy of less than 5 years, there are very few risks of treatment.

Endometrial cancer - If estrogen alone is taken by a woman who has a uterus, there is an increased risk of endometrial cancer (cancer of the lining of the uterus). This increased risk can be eliminated by the addition of a second hormone, a progestin, to the regimen. This is the reason it is important for a woman who has a uterus to be taking both hormones. Another important fact about endometrial cancer is that it is usually caught early and is rarely fatal. Because the primary symptom of this cancer is vaginal bleeding, your clinician will monitor you closely for any signs of unusual bleeding.

Breast cancer - There have been many studies done to look at whether hormones cause breast cancer in postmenopausal women. The studies do not agree. Some find no increased risk. Some find a small increased risk after many years (10 to 15 years or more) of regular use. With short-term therapy (less than 5 years), studies show that women are not at increased risk of breast cancer.

Are there different kinds of hormone replacement therapy?

Yes. Sometimes estrogen alone is prescribed, other times both estrogen and a progestin are prescribed. Most often, a woman will be given estrogen alone if she does not have her uterus (has had a hysterectomy). If the woman has a uterus, then she usually will take both estrogen and progestin. Hormones can be given in oral tablets, vaginal creams, or patches placed on the skin.

What are the side effects?

Side effects of estrogen include breast tenderness, edema, nausea, headache, and breakthrough bleeding. Progestins may cause fluid retention, acne, premenstrual-like symptoms, anxiety, depression, and irritability. These side effects are not medically serious, although they can be bothersome, and can often be helped by changing the dose or medication.

How do I know if hormone replacement therapy is right for me?

There is no question that short-term therapy will help relieve menopausal symptoms. Whether or not you will benefit from taking hormones for many years to prevent disease and prolong life must be based on your risk factor profile.

It's important to discuss the risks and benefits of therapy with your physician so that you understand how they apply to you. For example, a woman at high risk of coronary heart disease or osteoporosis may benefit from long-term treatment even more than a woman not at risk of these diseases.