GNAS and hyperphosphatemia: This mechanism could explain the hyperphosphatemia and hypocalcemia observed in patients with pseudohypoparathyroidism caused by inactivating mutations of Gsα. Conversely, in patients with paternally inherited pseudopseudohypoparathyroidism (PPHP), their kidneys do not exhibit resistance to PTH, consistent with the preferential expression of Gsα maternal alleles in proximal renal tubules, thyroid, ovaries, and pituitary (15).