FGF23 and enthesopathy: Our current studies demonstrate that Achilles entheses from all groups of mice lacking 1,25D action, regardless of whether these mice are null for Fgf23 or Phex (C–/–, C–/–/Hyp, C–/–/F–/–, C–/–/F–/–/Hyp), have enhanced BMP and IHH signaling and ALP activity, thus confirming that impaired 1,25D signaling as a result of increased serum FGF23 levels in Hyp mice leads to enthesopathy.