CYP2R1 and type 1 diabetes mellitus: Genome-wide association studies(GWAS) have confirmed that distinct polymorphisms in genes involved in vitamin D metabolism may affect islet autoimmunity and risk of T1D, SNPs of important genes involved in synthesis (7-dehydrocholesterol reductase, DHCR7), hydroxylation (cytochrome P450 family 2 subfamily R member 1, CYP2R1), degradation (cytochrome P450 family 24 subfamily A member 1, CYP24A1) and transcription (vitamin D receptor, VDR) (14, 15).