The excessive level of FGF23 noted in hypophosphataemia was then shown to suppress 1,25-dihydroxyvitamin D levels and induce rickets or osteomalacia in humans and mice (Bai et al., 2004; Fukumoto and Yamashita., 2002; Shimada et al., 2001,2005). The gene discussed is FGF23; the disease is osteomalacia.