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Estrogen: a women's best friend? 

For her brain, it's looking that way. 

In the past decade, evidence has steadily mounted that estrogen is critical to a woman's mental functioning. It appears to enhance memory and the ability to process verbal information. Numerous studies also have concluded that it reduces a woman's chances of developing Alzheimer's disease. 

Last year a researcher at Washington University in St. Louis shared his suspicions that a woman's brain cells may be vulnerable to damage early in menopause, and that hormone therapy might protect against that. 
Elizabeth Hudek, a Kansas City area gynecologist, heard geriatrician Stanley Birge explain his theory to the North American Menopause Society last October. 

She remembers thinking, "it was so important, I almost fell out of my chair."

 
A certified menopause clinician, Hudek is now convinced that protecting the brain is the "major benefit" of estrogen therapy. 

Although theories abound concerning estrogen's role in the brain, research findings are still considered inconclusive. A pair of groundbreaking studies under way may change that. 

The studies, involving thousands of women across the country, are expected to answer the nagging question of which women should take replacement hormones, according to Susan Resnick. She's an experimental neuro-psychologist who researches estrogen's effect on the brain for the National Institute on Aging in Baltimore. 

The studies of hormone replacement and brain function are an extension of the Women's Health Initiative, a 15-year nationwide study managed by the National Institutes of Health. Researchers are investigating the impact of hormone therapy, diet and supplementary calcium and vitamin D on osteoporosis, heart disease and cancer in older women. Results are expected in 2005. 

The health initiative is significant because it is the first time researchers have given either a hormone or a placebo to a large number of randomly selected women and monitored health effects many years later. 

What estrogen does 

Estrogen is the primary female sex hormone and is manufactured mostly in the ovaries. 

Although it is derived from testosterone, the primary male sex hormone, and is present in men in small quantities, estrogen accounts for many of the differences between the sexes. 

Most obviously, it controls a woman's reproductive system. But estrogen interacts with cells and systems throughout the body, including the brain, the bones and the cardiovascular system. 

Researchers have established that estrogen acts on the brain in several ways, including: 

• Increasing blood flow, and hence the supply of oxygen and glucose that the brain needs to function. 

• Boosting the amount of several brain chemicals - including acetylcholine, which plays a critical role in memory, and serotonin, which helps to maintain a good mood. 

• Increasing the number of synapses, or connections, between nerve cells in the hippocampus, where memory resides. 

• Helping neurons, or nerve cells, to grow and regenerate. 

• Decreasing inflammation, a process that appears to hasten aging. 

'An area vulnerable to aging' 

Barbara Sherwin, a psychology, obstetrics and gynecology professor at McGill University in Montreal, has researched the estrogen-brain connection for 20 years. Many studies have demonstrated that estrogen has beneficial effects on verbal learning and memory in women, she said. 

"This is an area of cognition that is vulnerable to aging," she said. 

"We've done studies on women who were pre-menopausal and needed their ovaries and uterus removed. Afterward, we gave them estrogen or a placebo. The ability to perform was maintained in the women who got estrogen after their surgery. We showed decreases in verbal learning and memory in the women who had gotten a placebo." 

Most women can expect some normal deterioration after menopause and with increasing age. But it's been shown that estrogen can prevent that deterioration - as it does with bone density, Sherwin said. 

An Alzheimer's link 

There are indicators that estrogen not only staves off some predictable cognitive losses in women, but also greatly decreases the odds of developing Alzheimer's disease. 

A majority of the dozen or so studies on estrogen and Alzheimer's have concluded there's a close relationship, according to Claire Warga in her 1999 book, "Menopause and the Mind."