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

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).

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 χ² 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.

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.

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.