Ionized calcium and PTH as predictors of hypoparathyroidism following total thyroidectomy.

Purpose: Post-surgical hypoparathyroidism (POSH) is a common complication after total thyroidectomy. This study aims to assess the accuracy of serum and ionized calcium and PTH levels on the first postoperative day (POD-1) to predict postoperative hypocalcemia (PoHC), transient hypoparathyroidism (THPT), and permanent hypoparathyroidism (PtHPT).

Methods: Biochemical parameters and clinical variables were retrospectively analyzed in 200 patients. The optimal cut-off points were determined using ROC curve analysis. Results were correlated with analytical and clinical variables and patient outcomes.

Results: PoHC incidence in POD-1 was 46%; THPT and PtHPT were 37 and 9%, respectively. Ionized calcium < 4.43 mg/dL on POD-1 predicted PoHC (AUC = 0.9) better than PTH and serum calcium. PTH < 8.06 pg/mL on POD-1 predicted PtHPT (AUC = 0.797). Multivariate analysis identified PTH < 21.2 pg/mL, ionized calcium < 4.43 mg/dL, and serum calcium < 8.76 mg/dL on POD-1 as significant PoHC risk factors.

Conclusion: Ionized calcium on POD-1 predicts PoHC accurately, while serum PTH indicates higher risk for PtHPT.