KL and hypercalcemia disease: In mice and men, loss of FGF23function leads to a severe phenotype characterized by elevated circulating vitamin D hormonelevels, early lethality, hypercalcemia, hyperphosphatemia, and soft tissue calcifications.Lack of the co-receptor α-Klotho causes a similar phenotype in humans and mice (Kuro-o et al. 1997; Ichikawa et al. 2007).