IGF1R and Parkinson disease: The substantia nigra is one of the brain regions with highest density of IGF-1 receptors (IGF-1R) [9], and IGF-1 has been found to increase survival of dopaminergic neurons both in vitro and in animal models of PD [13, 14]; however, increased levels of IGF-1 have been observed in the serum and cerebrospinal fluid of PD patients, which has been suggested a as possible marker for risk and early diagnosis of PD [15, 16].