There was a sense of deja vu surrounding the announcement by the National Institutes of Health (NIH) last week that it had called a halt to a major study of the health effects of long-term estrogen use. Didn't we already know that hormone-replacement therapy, when administered for more than a couple of years, was a bad idea?
Well, yes and no. Two years ago, the NIH cut short the part of the Women's Health Initiative (WHI) study that looked at the long-term use of a combination treatment including estrogen and progestin. Reason: women in the study were showing increased risk of heart disease, stroke and breast cancer. Last week's announcement concerns estrogen alone, which, it turns out, slightly increases a woman's risk of stroke but not of heart disease or breast cancer.
The difference between the two treatments is crucial because estrogen alone is taken by a lot more women in the U.S. (a total of 5.6 million, if you're counting) than the estrogen-progestin combination (2 million). Since estrogen in the absence of progestin increases a woman's risk of uterine cancer, it's given to women who have had a hysterectomy.
The higher stroke risk was comparable to what researchers had seen for the estrogen-progestin combo. Even at that, the increase was rather slight--about 8 additional strokes per 10,000 women. "Women should not feel this is some grand emergency for them," says Dr. Barbara Alving, director of the WHI.
In fact, what surprised scientists about the study is that supplements of estrogen, unlike the combination of estrogen and progestin, did not appear to increase a woman's risk of breast cancer. Perhaps estrogen pills work more selectively in the body than anyone had realized. Or perhaps the type of progestin used in studies was more likely to trigger tumor growth.
At any rate, what's now clear is that hormone supplementation--estrogen alone or in combination--is best suited for short-term relief (two years or less) of moderate to severe menopausal symptoms. As with any treatment, it's up to women and their doctors to weigh the risks--slight but very real--against the potential benefits.