CYP27B1 and type 1 diabetes mellitus: The onset of T1DM might also be related to polymorphism in the CYP27B1 gene located on chromosome 12, where polymorphisms in the CYP27B1 gene could lead to reduced levels of 1α-hydroxylase, thereby affecting the conversion of vitamin D to 1,25(OH)2D3 and increasing the susceptibility to T1DM (79).