GPX1 and autism spectrum disorder: The higher level of GSSG observed in the serum of many children with autism spectrum disorders [46-48,50,85,87,91] is likely to truly reflect increased oxidative stress as there is no significant difference in GPx-1 activity in serum or platelets [63,84] and GPx-1 is significantly lower in the erythrocytes of children with autistic disorder compared to controls.