Risk factors and prediction of postoperative hypoparathyroidism among patients with papillary thyroid carcinoma

BACKGROUND: We aimed to study the incidence rate of hypoparathyroidism, its risk factors, and identify its predictive factors among patients with papillary thyroid carcinoma (PTC) who had undergone total or near-total thyroidectomy and central neck dissection (CND). METHODS: Ninety-three PTC patients who had undergone total or near-total thyroidectomy and CND were analyzed for hypoparathyroidism. The association between clinicopathological factors and hypoparathyroidism was tested by χ(2) test and multivariate logistic regression. The ROC curve and a 2×2 contingency table were used to evaluate the performance of postoperative parathyroid hormone (PTH) and serum calcium concentration in prediction of hypothyroidism. RESULTS: Hypothyroidism was observed in 46 patients (49.5%), among whom 2 had permanent hypothyroidism. Univariate analysis showed that tumor size (P=0.034), extraglandular invasion (P=0.028), bilateral tumors (P=0.045), and bilateral CND (P=0.028) were significant risk factors of hypothyroidism. Multivariate analysis showed that extraglandular invasion (P=0.003) and bilateral CND (P=0.044) were independent risk factors. The patients with hypothyroidism had an average PTH level of 8.51 ng/L on the first day after surgery, and those without, 21.39 ng/L (P<0.001). When the PTH level on the first day after surgery was used to predict postoperative hypothyroidism, the ROC curve analysis showed that the area under curve (AUC) was 0.875. CONCLUSIONS: Hypothyroidism is a common complication of total or near-total thyroidectomy and CND, for which extraglandular invasion and bilateral CND are independently significant risk factors and the level of PTH is a reliable and early predictor.