2.Tetany, epilepsy, neuro-psychiatrical symptoms, hypocalcemia, hyperphosphatemia were common clinical manifestation.There was also low level of PTH, except pseudohypoparathyroidism.
6.All right, so since, again, parathyroid hormone causes excretion of phosphate and reabsorption of calcium, then another cause of hyperphosphatemia is hypoparathyroidism, when the parathyroid glands don't produce enough parathyroid hormone in the first place.