FGF23 and X-linked hypophosphatemia: Supporting the notion that there are multiple pathways involved in FGF-23 upregulation beyond phosphate sensing or HIF1α, conditional deletion of HIFα (HIF1α/Osteocalcin (OCN)-Cre) does not reduce FGF-23 levels in the Hyp mice (64), an animal model of X-linked hypophosphatemia (XLH).