PTH and Hypocalcemia: A recent statement on hypoparathyroidism of the American Thyroid Association found that the timing of PTH measurements in published studies has ranged from 10 min to 24 h post-thyroidectomy [14], and that a postoperative PTH level < 15 pg/mL is usually predictive of hypocalcemia [6,8,9,10,11,13,20,21].