Preoperative parathyroid hormone levels as a predictor of postthyroidectomy hypocalcemia.

Objectives. The goal of the present study is to determine whether a decline in the 1-hour postoperative parathyroid hormone (PTH) level relative to the preoperative level is predictive of hypocalcemia. Methods. This is a retrospective study involving 142 consecutive patients who underwent total thyroidectomy. Changes in preoperative PTH levels were then compared with the 1-hour levels. Results. Thirty-four of 142 patients (23.9%) who underwent total thyroidectomy developed hypocalcemia. Thirty-one of the 34 patients who became hypocalcemic had a 1-hour postoperative PTH drop of 70% or more when compared with the preoperative value (sensitivity = 91%, specificity = 98%, positive predictive value = 94%, and negative predictive value = 97%). Conclusion. A decline in the preoperative PTH level of 70% or greater at 1 hour following total thyroidectomy appears to be a reliable predictor of patients at risk of developing hypocalcemia. By allowing thyroid surgeons to identify these patients in the early postoperative period, calcium supplementation can be initiated sooner.