FGF23 and X-linked hypophosphatemia: However, deletion of Cyp27b1 in F–/– and F–/–/Hyp mice (C–/–/F–/– and C–/–/F–/–/Hyp) resulted in increased BMP and IHH signaling in entheses, similar to that seen in Hyp and C–/– control mice, thus demonstrating that impaired 1,25D production due to elevated FGF23 levels, not actions specific to FGF23, results in XLH enthesopathy.