GNAS and McCune-Albright syndrome: While the latter findings are consistent with the role of Gsα in mediating the phosphaturic actions of parathyroid hormone in the renal proximal tubule, recent data shows that serum phosphate in MAS patients is negatively correlated with the level of fibroblast growth factor-23 [116-118], suggesting that the elevation of this phosphaturic factor is responsible, at least partly, for the hypophosphatemia observed in these patients.