Evaluating the predictive value of early postoperative parathyroid hormone levels for hypocalcemia in total thyroidectomy patients: a retrospective cohort study

Background: Hypocalcemia is a common complication following total thyroidectomy, often resulting from transient or permanent parathyroid gland dysfunction. Identifying early predictors is essential to prevent morbidity and guide timely supplementation. The retrospective single-center study evaluated the predictive value of immediate postoperative parathyroid hormone (PTH) levels for early hypocalcemia. Methods: A total of 54 patients aged ≥18 years were included. PTH was measured within 1 hour postoperatively, while baseline serum calcium (Ca) levels were monitored every 8 hours for 24-48 hours. Patients were categorized by PTH level as low (<10 pg/ml), borderline (10-20 pg/ml), or normal (>20 pg/ml). Hypocalcemia was defined as Ca <8 mg/dl. Statistical analyses included the Kruskal-Wallis test with Tukey adjustment and Chi-square or Fisher’s exact test. Results: Most patients had normal PTH levels (77.8%, n=42), and hypocalcemia occurred in 20.4% (n=11). A significant association was observed between low PTH levels and hypocalcemia, with 66.7% of patients with low PTH developing hypocalcemia compared to 9.5% in the normal group (p=0.0022). ROC curve analysis using a PTH cutoff of <20 pg/mL yielded an AUC of 0.76, with 58.3% sensitivity and 90.5% specificity. Pairwise comparisons showed that low PTH (Mdn=7.67, IQR=1.2, p<0.001) differed significantly from normal PTH but not from borderline low PTH (p=0.436). A significant difference was also observed between borderline low and normal PTH (p=0.0313). Conclusions: Early postoperative PTH measurement is a valuable predictor of hypocalcemia after thyroidectomy. Patients with PTH ≤20 pg/ml should be closely monitored and managed proactively to ensure safe recovery and facilitate early discharge.