CYP2R1 and type 2 diabetes mellitus: Prior studies have established associations between certain vitamin D pathway polymorphisms, particularly in GC (e.g., rs4588, rs7041, rs2282679) and CYP2R1 (e.g., rs10741657, rs12794714, rs1993116, rs10766197), and metabolic syndrome and type 2 diabetes mellitus (T2DM) (20–23).