Hypophosphatemia leads to rickets by inhibiting mineralisation and apoptosis of hypertrophic chondrocytes [89], yet the contributions of FGF23 to hypophosphatemia are mediated by a complex network of pathways that ultimately increase urinary wasting, due to downregulation of the renal sodium-phosphate co-transporters NPT2A and NPT2C [90, 91], and decrease intestinal absorption of phosphate (Fig. 5a) [80, 81]. The gene discussed is FGF23; the disease is hypophosphatemia.