FGF23 and X-linked hypophosphatemia: Because FGF23 overexpression is unlikely to be the only consequence of the PHEX mutation (20), ablation of both Cyp27b1 and Fgf23 in Hyp mice (C–/–F–/–/Hyp) will further elucidate if 1,25D- and FGF23-independent effects of the PHEX mutation influence XLH enthesopathy pathogenesis.