CYP2R1 and type 1 diabetes mellitus: Cooper et al. [20] linked the genetic determinants of circulating 25(OH)D (DHCR7 and CYP2R1, which encode 7-dehydrocholesterol reductase and 25-hydroxylase) and vitamin D signaling in T cells (CYP27B1) with risk of T1D, while others (including a meta-analysis of nine studies with 1053 patients and 1017 controls) have linked specific polymorphisms of the VDR gene with risk for T1D [21].