Chronic exposure to estrogen impairs some cognitive functions

The researchers had not expected to see such pronounced results. In fact, the study had been designed to give them baseline information for a separate inquiry into the effects of soybean estrogens on cognitive function. They planned to compare the effects of chronic estradiol exposure to the effects of chronic exposure to genistein, a phytoestrogen found in soybeans. Genistein is believed to have similar effects in the body as natural or synthetic estrogens, although no study has definitively proven that it does.

Schantz and her colleagues had focused on the prefrontal cortex because it is rich in estrogen receptor beta (ER-beta), a protein that spurs gene expression and other activities in the cell when it binds to estradiol. Genistein also activates ER-beta.

Some women take genistein supplements or eat soy-based foods to reduce hot flashes or other symptoms of menopause, Schantz said.

"Women take them thinking they'll be a safe alternative to hormone-replacement therapy and they might help hot flashes," she said.

Those who have heard that hormone replacement can improve cardiac or brain function also hope that eating soy or taking genistein supplements will have the same effects, she said.

The effects of hormone replacement therapy (HRT) are more complex – and problematic – than once thought. A recent large-scale study of HRT in post-menopausal women was stopped because of an increased risk of stroke and blood clots in women taking estrogen alone, and a higher than average incidence of breast cancer, cardiovascular disease, blood clots and stroke in women taking estrogen and progesterone.

Studies of estrogen's effects on cognition have also had mixed results. In earlier studies, for example, psychology professor Donna Korol, a collaborator on the current project, found that estradiol enhances some abilities, such as place or spatial learning, while hindering others, such as learning that relies on stimulus-response associations, considered by some to be akin to "habit" and not fluid thought.

Performance in these tasks involves brain structures outside the prefrontal cortex.

The research indicates that multiple factors influence the effects of estradiol on the brain, Schantz said. The timing of the exposure, the types of brain functions or structures studied and the age of the test subjects can all generate different results, she said.

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Editor's note: To reach Susan Schantz, call 217-333-6230; e-mail: .

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