Though the long-term effects of hormone replacement therapy could not be measured by the new research, it did offer some reassuring findings. It suggested that some women's cholesterol profiles and metabolic function might improve on hormone replacement therapy and that blood pressure did not rise during or after a relatively brief stay on hormone replacement.
Participants taking oral hormone replacement pills reported, on average, a slight improvement in their ability to recall printed materials they had read. But for women who received hormones through a transdermal patch, subjective reports of memory problems increased slightly, as did their severity.
As expected, women who got hormone replacement maintained more bone density than those who did not.
The results from the Kronos Early Estrogen Prevention Study, known as KEEPS, were presented Wednesday at the North American Menopause Society's annual meeting in Orlando, Fla.
The study is likely to fuel a growing willingness among American women and their physicians to turn to replacement hormones, after a long period of decline following the release of the landmark Women's Health Initiative study about a decade ago.
The large and comprehensive Women's Health Initiative included 16,000 women and linked hormone replacement with higher risks of breast cancer and dementia. It also found increases in blood pressure and higher rates of stroke among women who took hormone replacement therapy.
But later assessments of the data suggested that some of those effects may have been magnified by the fact that some study participants were women in their 60s and 70s who continued taking hormone replacements for many years after their menopausal symptoms would probably have receded on their own.
In the much smaller KEEPS study, 727 younger women who were uniformly healthy at the outset were assigned to one of three groups: a placebo group and two groups that took different doses and formulations of hormone replacement than those used by most women who participated in the Women's Health Initiative study.
One of the intervention groups took 0.45 milligram per day of oral conjugated equine estrogens (commercially marketed as Premarin) for four years. A second group got a form of estradiol administered transdermally (better known as the Climara patch) for four years. Both intervention groups also got progesterone (available by the trade name Prometrium) for 12 days each month.
The researchers found subtle differences between the women on the patch and those taking daily pills. Women on the pills saw their LDL, or "bad" cholesterol, fall and their HDL, or "good" cholesterol, rise. But their triglycerides, a predictor of heart disease, also rose.
The patch improved blood glucose and insulin sensitivity - markers for Type 2 diabetes - in those who wore it. Oral hormones did not.
The participants in the KEEPS study ranged in age from 42 to 58. That made them younger, on average, than participants in the Women's Health Initiative study. All of the KEEPS participants were either perimenopausal or within three years of the onset of menopause, defined as a year after a woman has experienced her last menstrual cycle.
Dr. Mary Whooley, professor of medicine at the University of California, San Francisco, who was not involved in the study, called it important and said it underscored that use of hormone therapy "needs to be addressed on a patient-by-patient basis."
For women with cardiovascular disease or diabetes - or who are at higher than normal risk of developing those conditions - "we would need to pause and consider whether using the hormone therapy is worth the risk of worsening" their prospects, she said.
Today, 1 in 5 postmenopausal American women uses hormone replacement therapy, mostly to treat symptoms such as hot flashes, night sweats and vaginal dryness. That is about half the rate in 2002, when 40 percent took hormones. But as revisions to the Women's Health Initiative have relaxed widespread reticence about the medications among women and their physicians, hormone use appears to be creeping back up.
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