FGF23 and metabolic disease: The recent identification of GALNT3 mutations in both HFTC and HHS patients (Figure 2c) (Topaz et al. 2004, Frishberg et al. 2005, 2007, Ichikawa et al. 2005, 2006, 2007, Campagnoli et al. 2006, Garringer et al. 2006, Specktor et al. 2006, Barbieri et al. 2007, Garringer et al. 2007) has revealed that these metabolic disorders result primarily from aberrant regulation of FGF23-mediated phosphaturia (Kato et al. 2006, Frishberg et al. 2007).