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Heart Disease Health Center

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Slight Increase in Heart Problems Seen in Estrogen Replacement Study

WebMD Health News

April 4, 2000 (Atlanta) -- Government researchers say they've mailed letters to 27,000 women involved in an estrogen replacement study, to inform them that during the first two years of treatment, those who took the hormone seemed to have a slightly higher chance of heart attack, stroke, or blood clot than women who took a placebo.

Fewer than 1% of the patients taking part in the study had any of these problems, say officials from the National Institutes of Health (NIH), which is conducting the study.

An estimated 16 million postmenopausal women already take hormone replacement therapy, either estrogen alone or combined with progestin. Hormone replacement can reduce menopausal symptoms, such as hot flashes and vaginal dryness, and reduce the risk of osteoporosis. Some previous studies suggested it reduced the risk of heart disease.

The finding is preliminary and the risk may even disappear after women have been taking the hormone for more than two years, according to an NIH press release.

But the frequency of these health problems was slightly higher in hormone-treated women than placebo-treated women, says Jacques E. Rossouw, MD, the acting director of the study. He refused to provide actual figures.

The study's safety monitoring board requested the participants be told of the results. Since the instances of these problems were felt to be infrequent, the study was permitted to continue and is scheduled to go on until 2005. In the letters, participants were told that estrogen has long been known to cause blood clots, but "these findings for heart attacks and strokes were not expected" when the women first jointed the landmark study. The women were urged not to withdraw.

"We really owe it to the public out there to continue so we have definitive answers," Rossouw says.

These preliminary findings add to the uncertainty of how much estrogen therapy can help women avoid the consequences of heart disease. Two other recent studies found it didn't help older women who already have heart disease. These studies also found slightly higher risk of worsening heart disease in the early years of treatment. But researchers still hope that giving women estrogen can prevent or delay heart disease from developing, something Rossouw's team is studying.

And experts stressed that it is too early to change how women and their doctors decide who should try estrogen -- already a complex decision.

"We don't know how this is going to play out," cautioned Elizabeth Ross, MD, of the American Heart Association. "I don't think there's anything here to make us change our clinical practice. ... It's a patient-to-patient decision."

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