CYP2R1 and vitamin D deficiency: IV 25(OH)D: NA SNPsIV-1 (vitamin D transport and metabolism): GC, CYP2R1, DHCR7, CYP24A1IV-2 (vitamin D metabolism): GC, CYP2R1, DHCR7, CYP24A1, SEC23A, AMDHD1IV-3 (expanded instrument: 63 additional loci associated with serum vitamin D)IV-4 (vitamin D deficiency and insufficiency): GC, DHCR7, CYP2R1