A combination of measurements of serum 25(OH)D, 1,25(OH)2D, 24,25(OH)2D and C3-epi-25(OH)D might be necessary in the differential diagnosis of acquired- (e.g. granulomatous diseases), iatrogenic- (e.g. over-supplementation) and genetic causes (e.g. 24-hydroxylase deficiency) of non-PTH driven hypercalcemia. Here, PTH is linked to Hypercalcemia.