Estrogen Benefits Still in Question
March 20, 2001 -- Does taking hormone replacement therapy after menopause help prevent dementia and possibly Alzheimer's disease? Can the hormones increase a woman's risk for ovarian cancer? When it comes to the potential benefits, or risks, associated with hormone replacement therapy, it's hard to get a straight answer.
Three new studies in the March 21 issue of The Journal of the American Medical Association may help clear up some of the confusion, although not completely.
One complicated question: Does hormone replacement therapy, or HRT, actually protect women from mental decline as they age? Some studies have suggested it may. But numerous studies have tried to answer that question, and the results have still been mixed. Some studies have shown benefits on certain thinking and memory abilities, while others have shown no effect and some a harmful effect.
After evaluating dozens of studies identified in the medical literature from 1966-2000, Erin S. LeBlanc, MD, MPH, and colleagues found that only women with postmenopausal symptoms experienced improvements in thinking or memory while taking HRT. But the reasons for this are unclear and could be related to having fewer hot flashes and better sleep, compared with women not taking hormones.
LeBlanc and colleagues of Oregon Health Sciences University in Portland say the problem of the mixed messages is that most of the previous studies are flawed and conflicting, making it hard for women and their doctors to draw much conclusion from them about the value of hormones to protect against mental decline.
"Unfortunately, the message that has gotten out is that estrogen is of no value," says C. Dominique Toran-Allerand, MD, DSc, professor of neurobiology and behavior at Columbia University's College of Physicians and Surgeons in New York. "You can't say that on the basis of [the studies performed over the years], because those studies have been done incorrectly."
Toran-Allerand says that's because the estrogen in a woman's body is released on a carefully timed cycle, and no studies have tried to mimic that cycle after menopause to see if it protects women's brains.
Doctors are now making more of an effort to give women HRT that replicates that normal cycle, but many still receive estrogen on a continuous basis, which Toran-Allerand says can overload the estrogen receptors in the brain and make them less functional or kill them off. The receptors also become reduced in number or disappear when estrogen is stopped, such as in women who choose not to take hormones after menopause, she says.
Another study in the journal calls into question a fairly widely held belief that the natural estrogen to which a woman is exposed to before menopause plays an important role in protecting her from mental decline as she ages.