[Estrogens against Alzheimer disease? The female sexual hormone as a protective neurohormone].

The female sex hormone estrogen has a wide range of activities besides the sex-associated functions. Estrogen is a neurohormon. Its effects on structure and function of nerve cells is in the focus of research of basic neuroscience. In the brain estrogens not exclusively act via estrogen receptors but also receptor-independently. Estrogen can function dependent but also independent from estrogen receptors. In humans estrogen improves cognitive functions, learning and memory. In addition, beneficial effects of a hormone replacement therapy in prevention of Alzheimer's disease have been demonstrated. But on the basis of the current knowledge, estrogen is not a drug for the treatment of an already ongoing Alzheimer's disease process.