FGF23 and hyperphosphatemia: Compared with Klotho+/+ (WT) mice, KLKO mice exhibited high plasma concentrations of FGF23 and 1,25(OH)2D3, hyperphosphatemia, and hypercalciuria, but not ionized Ca or PTH, as described previously (Figure 1a–f) (Ohnishi et al., 2009a).