Since 1981 another explanation for the pathogenesis of AD has been proposed, named the neurotrophic factor hypothesis [8,9] represented by the nerve growth factor (NGF) hypothesis [10,11], according to which the altered neurotrophic status, usually supported by NGF and other neurotrophic factors (NTFs), affects AD progression [12,13]. The gene discussed is NTF3; the disease is Alzheimer disease.