Editor's Note: This article was originally published on Jan Hormone Replacement Therapy May Reduce Death Rate and Protect Against Heart Disease in Some Women (dateline January 16, 2001) | Breast Health News | Imaginis - The Women's Health & Wellness Resource Network

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Hormone Replacement Therapy May Reduce Death Rate and Protect Against Heart Disease in Some Women (dateline January 16, 2001)

Editor's Note: This article was originally published on January 11, 2001. However, the original title was misleading and has been modified to increase clarity.

There has been much debate in recent years about the benefits and risks of taking hormone replacement therapy (HRT). Now, researchers from the American Cancer Society have published the results of a large study of post-menopausal women that may help clarify some of the effects of HRT on heart disease and cancer.  According to lead researcher Carmen Rodriguez, MD and her colleagues, estrogen therapy may help reduce the number of deaths from cancer and offers protection against heart disease for thin women (see below).

Before menopause, the female body produces the hormones estrogen and progesterone in the ovaries. When a women reaches menopause, her estrogen and progesterone levels are reduced, and she may experience hot flashes, vaginal dryness, sleep disturbances, or other symptoms. HRT is designed to replace the hormones lost at menopause. HRT regimens contain estrogen, progestin (a synthetic form of progesterone), or a combination of the two. Most physicians recommend that women take a combination of estrogen or progestin because taking estrogen alone may increase the risk of endometrial cancer (cancer of the uterine lining). Previous studies have shown that HRT reduce the risk of heart disease by lowering cholesterol.

In the American Cancer Society study, researchers analyzed the effects of estrogen on 290,827 healthy post-menopausal women from 1982 to 1994. None of the women had a history of cancer or cardiovascular disease when they enrolled in the study. After 12 years of follow-up, the overall death rate among the women who took estrogen replacement therapy was 20% lower than among those who did not take estrogen.

The researchers also found that thin women who took estrogen at the beginning of the study were 50% less likely to die from heart disease within 12 years compared with women who never used HRT. However, obese women did not receive any protection from heart disease from taking estrogen.

Researchers have previously found that estrogen helps protect women against heart disease. As a woman ages, her risk of heart disease increases: 9,000 American women under age 45 (before menopause) have heart attacks each year versus 250,000 women over age 65 (after menopause). Estrogen also appears to help maintain low cholesterol levels and improve the arteries’ flexibility and expandability.

According to Dr. Rodriguez, after menopause, a woman’s fat cells (adipose tissue) are her main source of estrogen. Since obese women have more adipose tissue, they already have a higher amount of estrogen than thinner women, and thus the amount of estrogen added with HRT is usually not enough to have a significant impact against heart disease. This is unfortunate because obese women are at a higher risk of heart disease than thinner women for reasons unrelated to estrogen levels, said Dr. Rodriguez in an American Cancer Society news report. Therefore, obese women may need to consider other options besides HRT to help protect against heart disease.

A body mass index measures a person’s total body fat and is derived by multiplying a person's weight in pounds by 703 and then dividing it twice by the person’s height in inches. According to federal guidelines, women who have BMIs between 25 and 30 are considered overweight and women with BMIs of over 30 are considered obese.

Besides relieving menopausal symptoms and helping to protect thin women against heart disease, HRT can also help prevent and treat osteoporosis, a degenerative bone disease that affects approximately one half of all women over age 50. However, there has been controversy over whether or not HRT increases the risk of breast cancer.  According to Dr. Rodriguez, thin women who use HRT may have a higher risk of breast cancer than obese women because the amount of estrogen added with HRT is significant for thin women compared with the amount of estrogen added for obese women.

However, in the American Cancer Society study, which ran from 1982-1994, the researchers did not find an increased risk of death from breast cancer among the women who took HRT, regardless of their weight. In the study, the women were likely to receive close monitoring by physicians, increasing the chances that breast cancer would be detected and successfully treated at an early stage.

Although studies have been inconsistent, there appears to be an emerging consensus that HRT does not significantly increase the risk for breast cancer, at least for women who take estrogen less than five years or who take less than 0.625 mg per day. The Women’s Health Initiative (WHI) is currently conducting a large study on HRT. The WHI study is a 15-year clinical trial that is investigating HRT, heart disease, osteoporosis, breast cancer, and colon cancer in 63,000 American women between the ages of 50 and 79. The results of the study will help to answer many questions about the benefits and risks of HRT. In the meantime, women should discuss the benefits and risks of taking HRT with their physicians, based on their individual medical situations.

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