PTH and Hypocalcemia: Moreover, there is no consensus on the most useful predictive cut-off point for post-operative PTH levels and the appropriate time of PTH measurement after surgery: 1 h PTH level after skin closure may be predictive of postoperative hypocalcemia [6,8,9,10,11,13], while other studies suggested that a reduction in postoperative PTH of more than 44% [17] or more than 60% [18] is predictive of temporary biochemical hypocalcemia [7,14,19].