IGF1 and Alzheimer disease: Indeed, the sustained dysfunction of insulin/IGF-1 signaling within the central nervous system negatively impacts cell functionality and viability, thus triggering a pathogenetic cascade, as observed in Alzheimer’s disease (AD), Parkinson’s disease (PD), Huntington’s disease (HD), amyotrophic lateral sclerosis (ALS), and multiple sclerosis (MS) (66).