1998) used induced hypocalcemia followed by a brief return to normocalcemia and a subsequent hypocalcemia to analyze PTH hysteresis effects. After a sharp increase of PTH during the first peak of 0.8 mg/dl from Ca2+ baseline levels and a slight drop due to the return to normal, the authors did not observe a second transient PTH peak (Fig. 9). This evidence concerns the gene PTH and Hypocalcemia.