PTH and Hypocalcemia: In these studies the rapid recovery of plasma Ca2+ was examined after a brief induction of hypocalcemia with an EGTA infusion in parathyroidectomized (PTX), thyroidectomized (TX), thyroparathyroidectomized (TPTX) and calcitriol depleted rats and rats treated with different doses of PTH, CT and calcitriol.