GDNF and early-onset autosomal dominant Alzheimer disease: In addition, since glial cells are implicated in the development, survival, and metabolism of neuronal cells (60) and modulate the synaptogenesis in the brain (61-63), therefore, progesterone by in vivo stimulation of GDNF secretion from glial cells may be proved to be beneficial for neurodegenerative disorders such as Alzheimer’s disease.