The genetic variants involved in vitamin D binding protein cause discrepant effects on free versus total 25(OH)D concentration [16,17], and variants affecting the catabolism of vitamin D (CYP24A1) also influence plasma concentrations of phosphate and FGF-23 [18], such that these genetic variants may affect diabetes independent of their effects on 25(OH)D concentration. This evidence concerns the gene GC and diabetes mellitus.