The intimate relationship between Pi metabolism and PiT/FGF/FGFR signalling may have broader implications for diseases with altered systemic Pi levels such as chronic kidney disease and x-linked hypophosphatemic rickets that are characterised by increased FGF23 serum levels (Bon et al., 2018b; Kinoshita and Fukumoto, 2018; Wolf, 2012). This evidence concerns the gene FGF23 and X-linked hypophosphatemic rickets.