Both Fgf23−/− and Klotho deficient mice share many similarities such as hyperphosphatemia, high 1,25(OH)2D3 levels, ectopic ossification in the soft tissues, and several lines of compelling evidence suggest that FGF23’s function in the regulation of systemic phosphate and vitamin D homeostasis is klotho-dependent [3], [21], [50]. The gene discussed is FGF23; the disease is hyperphosphatemia.