Estrogen effects on neuronal morphology.

This review focuses on the effects of estrogen on neuronal morphology. Over the last decade neuroscientists have accumulated a wealth of information confirming the trophic effects of 17beta-estradiol on a variety of brain regions, including changes of hippocampal spine density and axonal outgrowth and retraction in hypothalamic nuclei, as well as other measures of structural reorganization that could underlie some of the cognitive benefits attributed to this hormone. Overall, results from a variety of investigators suggest that 17beta-estradiol is a potent structural signal that can drive developmental as well as adult plastic events in a variety of brain regions, not only those implicated in reproduction, but also in a diversity of functions. Most notably, these structural modifications that subserve cyclic physiological processes, can also be activated in other brain regions to protect and even reverse structural neurodegenerative processes. The data presented here are not exhaustive, but rather meant to provide a few examples of these structural effects of 17beta-estradiol that could have important implications for clinical practice.