CYP2R1 and type 1 diabetes mellitus: We confirmed that CYP2R1 (rs1993116) increases the risk of T1D, but CYP2R1 (rs12794714) does not, The probable reason is that Since rs12794714 is located in an intronic region, these synonymous variants do not alter the protein sequence and therefore have minimal impact on 25-hydroxylase activity and function (33).