But these studies reveal only that women who take estrogen have lower rates of heart attacks, not that the hormone medication protected them, explains Jacques Rossouw, M.D., of the National Institutes of Health in Bethesda, Md. He's acting director of the large Women's Health Initiative study. In those earlier observational studies, researchers followed women who had chosen either to take the drug or to not use it. The researchers didn't assign the medication or a placebo to similar groups of women, as they would in a "clinical" trial.
Indeed, women who opt for estrogen tend to be healthier than nonusers even before starting the drug. Also, women who actually take the medication regularly are "doing a bunch of other things that are keeping them healthy," Rossouw said. They eat a good diet, exercise and watch their weight. Many women, who are prescribed estrogen, never fill their first prescription or they don't stay on the drug for longer than a year, studies show.
When scientists began designing the Women's Health Initiative, other researchers "didn't even think we should examine the cardiac question," said Rossouw, because they were convinced of estrogen's benefit to the heart. Now many doctors eagerly await the study's findings, due out in 2005.
Take an Accounting
Women need to know whether or not estrogen helps the heart, so they can write an accurate list of its pros and cons before deciding whether or not to use it. The drug helps reduce osteoporosis, and that's high on many women's list of concerns. No one wants to end up with a broken hip or hunched over in pain. But the drug also comes with serious risks and side effects.
In some women, estrogen causes menstrual — like bleeding, headaches, nausea, vaginal discharge, fluid retention, swollen breasts, weight gain, breast tenderness, depression, or blood clots. Because of such side effects, doctors often advise women who have high blood pressure, diabetes, liver disease, blood-clotting disorders, seizures, migraine headaches, gall-bladder disease, or a history of cancer to stay off the medication.
Daughters of mothers who took DES (diethylstilbestrol) during pregnancy are also advised against it. Taking estrogen for more than five to 10 years may increase the risk of developing breast cancer by 40 percent, recent studies show. However, it's not just taking estrogen medication that ups the odds of cancer. A woman's likelihood of getting breast cancer increases two to three percent every year prior to menopause, because of the estrogen her body produces naturally, Rossouw noted.
Early studies suggested that taking progesterone with estrogen throughout the month, instead of for just part of the month, eliminates the breast cancer risk. Whether this is true "remains unresolved," Louise A. Brinton, Ph.D., and Catherine Schairer, Ph.D., from the National Cancer Institute in Bethesda, Md., wrote in the August 9, 2000, Journal of the American Medical Association (JAMA). More researchers need to look into this question, the team notes.