Early parathyroid hormone (PTH) level as a predictor of post-surgical hypoparathyroidism.

Introduction: Post-operative hypocalcemia and postoperative persistent hypoparathyroidism remain the most common complications after thyroidectomy. Many approaches have been developed to prevent them, but actually, a common protocol is not yet individuated.
Materials and Methods: We retrospectively analyzed the results of a prospectively collected database. We dosed PTH preoperatively and 4 h after surgery (PTH&#95;4); calcium was evaluated preoperatively, on the first (I&#95;POD) and on the second postoperative day (II&#95;POD). Hypocalcemia was defined when calcium <8 mg/dl. PTH&#95;4 and I&#95;POD calcium serum levels are identified to predict postoperative hypocalcemia.
Results: Three hundred and forty-eight patients were enrolled, 37 patients resulted as hypocalcemic on I&#95;POD and 41 on the II&#95;POD. PTH&#95;4 is related to I&#95;POD ( p  < 0.001, r  = 0.45) and II&#95;POD ( p  < 0.001, r  = 0.44) calcemia. PTH&#95;4-cut-off predicting I&#95;POD hypocalcemia was 10.50 pg/ml (sensitivity: 78.7%, specificity: 72.7%). A PTH&#95;4 value of 11.5 pg/ml is able to predict hypocalcemia during II&#95;POD (sensitivity: 76.5%, specificity: 69.2%). We set up a combined test to predict II&#95;POD hypocalcemia, using PTH&#95;4 and I&#95;POD calcium (sensitivity: 77.8%, specificity: 89.9%).
Conclusion: This research shows the association between PTH&#95;4 and postoperative hypocalcemia. The PTH&#95;4 cut-off to predict I&#95;POD-hypocalcemia was 10.5 pg/ml. We analyzed the calcemia trend during the postoperative period and we realized a combined test using PTH&#95;4 and I&#95;POD-calcemia. This test improves the accuracy of the previous test. Further studies, in particular multicentric, with a larger sample are necessary to validate the combined model.