Using estrogen alone — as roughly 5.6 million women who've undergone hysterectomies do — doesn't appear as risky as taking it with the hormone progestin. Use of estrogen alone for seven years didn't increase women's risk of breast cancer or heart attacks, while taking the two-drug combination for even shorter periods did.
The findings, announced by the National Institutes of Health, may make it more difficult for women to decide whether to take some form of hormone therapy at menopause and, if so, for how long. Already Tuesday, gynecologists reported patients asking if they should abruptly quit their pills.
Estrogen, either alone or with progestin, remains the most effective treatment for such menopausal symptoms as hot flashes and night sweats. For now, the NIH's best advice: If you need it for that reason, take as low a dose as works, for as short a duration as possible.
CBS News Correspondent Elizabeth Kaledin reports the estrogen study is yet more evidence that puts hormones in their place. When it comes to preventing age-related disease, these drugs have failed. But they still play a role in the treatment of menopause that cannot be overlooked.
"This isn't an emergency," said Dr. Barbara Alving, director of the NIH's Women's Health Initiative. But for women who have used estrogen for many years, "this provides them with an opportunity to say, 'Do I really need to be on this still?"'
The big question is whether the stroke concern is relevant to today's average estrogen user, a 50-something woman. The average study participant was 70 and NIH didn't study menopause symptoms, only estrogen's effect on heart disease.
Also, women today can choose much lower estrogen doses than those that were studied, and no one yet knows if lower doses are safer.
"It certainly adds to the confusion, I'm sorry to say," said one of the study's leaders, Dr. Norman L. Lasser of the University of Medicine and Dentistry of New Jersey.
"It sounds cliche to say do more studies, but I don't think we should give up on estrogens," he added. If doctors could learn to predict who was most likely to have an estrogen-caused side effect, he said, other women could safely use it.
Other doctors stressed the good breast-cancer news.
"I think it's reassuring," said Dr. Catherine Stika, obstetrics and gynecology chief at Northwestern Memorial Hospital in Chicago, who wishes NIH had continued the study another year to completely settle the question. Still, "I can more confidently work with my (hysterectomy) patients ... and offer them the option of estrogen replacement for a short period of time — 'short' to be defined."
Only women who have undergone a hysterectomy can take estrogen alone; in other women, progestin prevents estrogen-spurred uterine cancer.
Doctors long thought that hormone therapy would keep women generally healthier after menopause, by reducing heart attacks and keeping the brain sharp.
But in 2002, a major NIH study concluded that the estrogen-progestin combination not only didn't prevent heart disease — but long-term use actually raised the risk of breast cancer, strokes and heart attacks. A second study found it increased the risk of dementia, too.
The news led women to quit using hormones in droves, from 15 million users of either estrogen or combination therapy in 2002 to 8.5 million today, according to leading hormone maker Wyeth Pharmaceuticals.
Until now, scientists weren't sure whether estrogen alone was as risky, holding out hope that maybe progestin was the culprit.
But Tuesday, the NIH ended its study of estrogen-only therapy, saying:
Estrogen alone increased the risk of a stroke as much as estrogen-progestin does. For every 10,000 women, those taking hormones suffered eight more strokes a year than women who didn't use hormones.
Preliminary data from a related study suggested women taking estrogen are more likely suffer dementia than those taking a placebo.
On the good side, estrogen alone clearly is less risky than combination therapy because it didn't increase odds of a heart attack or breast cancer, Lasser said.
Like combination therapy, estrogen alone also prevented bone-thinning osteoporosis, but NIH stressed that there are safer osteoporosis treatments.
"It really is true that this therapy needs to be individualized for every woman," with regular checks to see if menopause symptoms have diminished enough to quit, stressed Wyeth's Dr. Victoria Kusiak. "It's not a lifelong commitment."
The NIH released only preliminary data; details are scheduled to be published in a medical journal in mid-April.
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