The patients were part of the Women's Health Initiative, a major test of the risks and benefits of hormone replacement after menopause. The study was abruptly stopped in July 2002 when it became apparent that the dangers from hormones, particularly the higher risk of heart disease, outweighed any benefits.

Hormone therapy is no longer advised as preventive medicine for older women. However, the US Food and Drug Administration and the American College of Obstetricians and Gynecologists say that women with moderate to severe menopausal symptoms can use such therapy, but urge them to take the smallest dose possible for the shortest time possible.

The new study, appearing Wednesday in the Journal of the American Medical Association, emphasizes that hormone therapy may not be a permanent solution for menopausal symptoms in many women, and that multiple strategies may be needed.

"Women are learning that their symptoms might return, even after using these hormones for more than five years," said Sherry Sherman of the Geriatrics and Clinical Gerontology Program at the National Institute on Aging. It is one of several branches of the National Institutes of Health that collaborated on the study.

"Before this study, we knew little about the effects a woman experiences when she suddenly stops hormone-therapy use," Sherman added.

About 2 million American women enter menopause each year. Despite the long-term health risks, recent studies suggest that about 20 percent of post-menopausal women continue to use hormone therapy.

Menopausal Symptoms Return

The women in the trial stopped using the hormone combination of estrogen plus progestin in the summer of 2002. Between eight and 12 months later, a team led by Judith Ockene of the University of Massachusetts Medical School surveyed 8,405 study participants who took the combination or a placebo.

The women had been taking the drugs or the placebo for an average of 5.7 years, and their average age was 69.

Among those women with menopausal symptoms when they started taking the drugs, 55 percent had symptoms return, as did 21 percent who were taking placebos.

And "for women who do not have symptoms before they start HRT, it appears that discontinuing use does not induce these symptoms," the researchers said.

Moreover, Ockene said it's likely that for most women who stop hormone therapy, the symptoms eventually diminish -- something other recent small studies suggest, but which her study was not set up to answer.

Dr. Diana Petitti, a specialist on menopause treatment with Kaiser Permanente Southern California, noted in an accompanying editorial that "the high frequency of symptoms reported by the Women's Health Initiative participants may be a result of the abrupt withdrawal from hormone therapy.

"Thus, when it is time to consider discontinuing hormone therapy, gradual tapering of the dose would be a logical clinical strategy arising from these new observations," she added.

About half of those who were taking the hormones said they had either turned to other medicines, such as antidepressants, vitamins or herbal remedies, or alternative medicine like acupuncture after discontinuing hormones. A similar proportion said they turned to lifestyle changes -- new diet, more exercise, more use of fans or air conditioners, drinking less caffeine -- to help them deal with symptoms after the original trial stopped.

Only about 320 of the women, including 111 who took inactive pills, said they resumed HRT after the first trial, and most said it was to deal with symptoms or to treat or prevent osteoporosis.

Ockene and her colleagues concluded that any of the "wide range of lifestyle and medical strategies to manage symptoms may help." But they suggest that more testing should be done on all of them, and especially those involving alternative medicine, to determine what's really effective.