Predicting transient hypocalcemia in patients with unplanned parathyroidectomy after thyroidectomy

To assess the utility of rapid parathyroid hormone (PTH) values in predicting transient post-operative hypocalcemia in patients with unplanned parathyroidectomy during total or completion thyroidectomy.

All patients who underwent total or completion thyroidectomy between January 2010 and January 2015 were reviewed. Incidences of post-operative hypocalcemia were compared in patients with and without unplanned parathyroidectomy. Unplanned parathyroidectomy was defined as intra-operative incidental or intentional parathyroidectomy. Logistic regression assessed for predictors of hypocalcemia and optimum amount of calcium supplementation.

Thirty-eight (13.6%) patients had evidence of incidental parathyroidectomy and 39/280 (13.9%) patients had parathyroid autotransplantation intra-operatively. Central neck dissection and malignancy were identified as risk factors for unplanned parathyroidectomy (p = 0.001, p = 0.060). Patients with unplanned parathyroidectomy were more likely to have hypocalcemia (p = 0.002) and hypoparathyroidism (p < 0.0005). PTH value was the only significant predictor of hypocalcemia in these patients. In patients with a post-operative PTH of ≤15, initial calcium supplementation ≥ 1000 mg decreased the risk of hypocalcemia (p < 0.05).

Post-operative PTH value predicts hypocalcemia in patients undergoing total and completion thyroidectomy with unplanned parathyroidectomy. In patients with a post-operative PTH < 15, initial calcium supplementation with ≥1000 mg of elemental calcium is recommended.