Estrogens: mechanisms of neuroprotective effects.

Within the last few years, there has been a growing interest in the neuroprotective effects of estrogen and the possible beneficial effects of estrogen in neurodegenerative diseases such as stroke, Alzheimer's disease, and Parkinson's disease. The concept of neuroprotective effects of estrogen in women remains controversial because these effects may vary with the timing of treatment. Research increasingly suggests that changes in estrogen levels during aging may increase risk for Alzheimer's disease, the most common type of dementia. This update reviews the newest information about estrogen and cognitive aging, including information regarding the role of bioavailable estrogen in older women and men.