WASHINGTON (AP) -- For millions of women, the question of whether to take hormones after menopause just got more vexing: A major study concludes that long-term use of estrogen and progestin is dangerous. But hormones are the mainstay treatment for hot flashes and other menopause symptoms - so how long can women safely use them? And what about using just estrogen alone?

All the answers aren't in yet. But new results from the nation's biggest hormone study suggest many of the 6 million American women who use estrogen and progestin should quit - and the National Institutes of Health urged them Tuesday to talk with their doctors about what to do.

If you're using the hormone combination in hopes it will protect your heart, definitely quit, said Dr. Jacques Rossouw, acting director of NIH's Women's Health Initiative, which sponsored the study.

Contrary to once-popular belief, the pills can actually harm the hearts of previously healthy women, concluded the study of 16,600 women. They significantly increased the risk of a heart attack or stroke beginning in women's first year of hormone use. In addition, the risk of breast cancer jumped after four years of hormone use.

Other smaller studies had raised similar suspicions, but the new results were so convincing that the government abruptly halted the study Tuesday, three years ahead of schedule.

Here's the confusing part: The risks for each individual woman are actually pretty small. Compare 10,000 women who take the hormones for a year with a similar group that doesn't. Among the hormone-takers, an additional 8 women will get breast cancer, 7 will have a heart attack, 8 will have a stroke and 18 will have blood clots in the legs or lungs, another risk.

But consider that millions take hormones, and that quickly adds up to thousands of preventable illnesses.

On the good side, the hormones did prevent hip fractures from the brittle-bone disease osteoporosis, and lowered the risk of colon cancer. But there are safer alternatives that women should consider using instead, Rossouw said. Indeed, some doctors prescribe an osteoporosis drug marketed as an estrogen alternative, called raloxifene, believed to be safer for the heart and breast.

The real tricky issue: An estimated 40 percent of women use hormones because they're the only relief for the hot flashes and night sweats that can make menopause miserable. Those symptoms often last a year, longer for some women. So how long could they use estrogen and progestin?

"There is no really safe period," Rossouw acknowledged, noting that the heart risks occur rapidly. He advised "as short a period as you can get away with in order to manage the menopausal transition."

"We have a very slippery slope now when we talk about short-term benefits," added Marcia Stefanick of Stanford University, one of the study's lead researchers.

Will women quit hormones or brave the risks?

"The bottom line is we all have to choose our poison," said Shirley Sirota, 70, of Houston, who five years ago convinced her doctor to prescribe estrogen and progestin because osteoporosis drugs alone weren't enough for her very brittle bones.

Surprised at Tuesday's news, Sirota said she'll probably stick with the hormones because she fears a broken hip confining her to a wheelchair more than a heart attack or cancer.

Others may not be as sanguine. Dr. Steven R. Goldstein of New York University said he'd reassured seven worried patients Tuesday morning alone that the risks of short-term hormone use - the only way he prescribes them now - are very small.

"I'm sorry to hear it," study participant Jane Doyle, 65, said after researchers at Washington Hospital Center revealed the results to her Tuesday morning. Equally worried about osteoporosis and cancer, Doyle said she'll ask her own physician if she should continue taking hormones on her own.

Tuesday's warnings don't apply to the 8 million more American women who use estrogen alone - a therapy restricted to those who've had hysterectomies because estrogen causes uterine cancer unless balanced by progestin. The NIH is letting a second, smaller study of those women continue for now, saying the risks and benefits remain unclear.

Also, the study announced Tuesday tested only Prempro, the leading estrogen-progestin combination - not other brands that bear lower doses of estrogen or estrogen skin patches. Stefanick challenged the drug industry to prove whether they're any safer.

While hormone use has slowly declined for a decade, Rossouw said the biggest hurdle is drug industry marketing, both in ads patients see and promotions to doctors, that suggest hormones are great for overall health. "We hope that truth will win out over advertising," he said.

Copyright 2002 The Associated Press. All rights reserved.