A large number of studies have demonstrated several correlations between IGF-1 and PD: (1) high densities of IGF-1 receptors exist in the substantia nigra; (2) IGF-1 increases the survival of dopaminergic and substantia nigra neurons; (3) IGF-1 protects dopaminergic neurons from programmed cell apoptosis (Mashayekhi et al., 2010; Bernhard et al., 2016). This evidence concerns the gene IGF1 and Parkinson disease.