CYP2R1 and type 1 diabetes mellitus: Cooper et al. [18] studied variants in DHCR7, GC, CYP2R1 and CYP24A1 in British patients with type 1 diabetes and found associations only with DHCR7 and CYP2R1. In contrast, a study in the Danish population found no associations of these four loci with type 1 diabetes [19].