MTHFR and autism spectrum disorder: ASD: Autism Spectrum Disorder; AT: Autoimmune Thyroiditis; MTHFR: Methylenetetrahydrafolatreductase; TCN1: Transcobalamin 1; TCN2: Transcobalamin 2; MTRR: Methionine synthase reductase; PEMT: Phosphoethanolamine N-Methyltransferase.