Estrogen is a hormone that is dominant in the female reproductive system. In women, most
estrogen is produced by the ovaries. Men produce estrogen by converting testosterone into
estrogen. Because this hormone also has many beneficial effects on brain cells, it currently
is being studied as a treatment for Alzheimer's disease. The enzyme that forms the
neurotransmitter acetylcholine is promoted in the presence of estrogen. Several very small
clinical studies have demonstrated improvement in cognitive function and mood measures in
women with Alzheimer's disease who take estrogen.