Risks of Hormone Therapy

Short-term side effects: Some women report side effects from taking Hormone Therapy, including unusual vaginal discharge and bleeding, headaches, nausea, fluid retention and swollen breasts. Some women think hormone therapy will make them gain weight while taking hormone therapy, but research now shows this is not true. Some women do gain weight during menopause, but it is because their metabolism slows down as they age, and they many not be increasing their amount or level of physical activity. Short-term benefits or side effects should become apparent within weeks or months after treatment begins.

Long-term risks (These will not be readily apparent for each individual woman):
Cancer: There is concern that hormone therapy can increase the risk of some cancers. When estrogen is taken alone, it raises the risk of endometrial cancer (lining of the uterus). Adding progestin with estrogen (HT) can dramatically reduce this risk. Progestin is added to prevent the overgrowth (or hyperplasia) of cells in the lining of the uterus, so women who still have an intact uterus are generally given this combined therapy.

The National Institutes of Health's (NIH) Women's Health Initiative (WHI) stopped a major clinical trial early on July 9, 2002 due to finding an increased risk of invasive breast cancer from hormone therapy with estrogen and progestin. The increased risk of breast cancer appeared after 4 years of hormone use. After 5.2 years, estrogen plus progestin use resulted in a 26 percent increase in the risk of breast cancer-or 8 more breast cancers each year for every 10,000 women. Women who had used estrogen plus progestin before entering the study were more likely to develop breast cancer than others, indicating that the therapy may have a cumulative effect.

Regarding ovarian cancer, an observational study, supported by the NIH's National Cancer Institute (NCI), recently found that estrogen-only therapy appeared to increase the risk of ovarian cancer. But other, similar studies have not found such an increased risk, and the possible relationship between estrogen use and ovarian cancer remains unclear.

The decision to take hormone therapy should be based on an overall look at the risk and benefits and how they fit with your personal health profile.

Breast Density: Taking both estrogen and progestin also can affect a woman's breast density. Increased breast density from hormone therapy makes it more difficult for a radiologist to read some mammograms, leading to the need for follow-up mammograms or breast biopsies. Increased density also is a concern because other studies have shown that women age 45 and older whose mammograms show at least 75 percent dense tissue are at increased risk for breast cancer. However, it is not known if increased breast density due to hormone therapy carries the same risk for breast cancer as having naturally dense breasts.

Data from the Postmenopausal Estrogen/Progestin Interventions (PEPI) trial at NCI indicate that about 25 percent of women who use combined hormone therapy have an increase in breast density on their mammograms, compared to about 8 percent of women taking estrogen alone. One study showed that stopping hormone therapy for about 2 weeks before having a mammogram improved the readability of the mammogram. However, further research is needed to confirm the usefulness of this approach.

Heart Disease: In the past, taking hormone therapy (estrogen plus progestin) was thought to help protect women against heart disease. But recent findings from the Women's Health Initiative (WHI) study showed that taking hormone therapy poses more risks than benefits. The study found that hormone therapy could increase a woman's risk for heart disease, stroke, and pulmonary embolism (blood clot in the lung), as well as breast cancer. Because of these findings, the U.S. Preventive Services Task Force recommends that women who have gone through menopause should not be given hormone therapy to prevent heart disease and other chronic conditions. The WHI is also looking at the effect of taking estrogen alone (this is given to women who have had a hysterectomy, or no longer have a uterus, or womb) on heart disease and other conditions; results should be available in the next few years, or sooner.

Earlier studies have also shown that women who have gone through menopause and who have heart disease, may have a greater risk of another cardiac event (like heart attack) after starting hormone therapy, at least in the short-term. For women who have had strokes, their risk for having another stroke goes up when they start taking hormone therapy. Hormones are not recommended for women with heart disease or for women who have had a stroke. If you have gone through menopause, talk with your health care provider about whether hormones are right for you.

If you are taking hormone therapy, watch for signs of trouble, such as abnormal bleeding, breast lumps, shortness of breath, dizziness, severe headaches, pain in your calves or chest, and report them to your health care provider right away. Also, talk with your health care provider about how often you should have an exam.