Postoperative normocalcemic hyperparathyroidism: a comprehensive analysis of 510 cases

Postoperative normocalcemic hyperparathyroidism (NC-HPT) is defined as elevated parathyroid hormone (PTH) levels despite normal calcium levels after parathyroidectomy for primary hyperparathyroidism (PHPT). This study investigates the demographic, biochemical, and histopathological factors associated with NC-HPT in a large patient cohort and presents the follow-up outcomes.

The initial study sample included 571 patients who underwent surgery for PHPT between January 2018 and January 2024, 510 of whom were analyzed retrospectively after the application of the exclusion criteria. Preoperative and postoperative biochemical parameters, bone mineral density, pathological findings, and follow-up data were evaluated. NC-HPT was defined as postoperative PTH elevation in the presence of normocalcemia. Logistic regression and receiver operating characteristic curve analyses were performed.

NC-HPT developed in 104 (20.4%) of the 510 patients analyzed in the study. The condition peaked in the third postoperative month and then gradually declined, with 86.5% of cases resolving by month 30. Univariate analysis revealed elevated preoperative PTH, high alkaline phosphatase (ALP), and parathyroid hyperplasia to be significant predictors. In multivariate analysis, only preoperative PTH level (OR: 1.003; 95% CI: 1.002-1.005; p < 0.001) and hyperplasia (OR: 3.311; 95% CI: 1.277-8.547) remained independent risk factors. ROC analysis identified a preoperative PTH cutoff value of 298 pg/mL with an AUC of 0.665 (95% CI: 0.608-0.723). No significant associations were observed with other demographic, biochemical, or radiological parameters.

NC-HPT occurs in approximately 20% of patients undergoing surgery for PHPT but often resolves during follow-up. Elevated preoperative PTH levels and parathyroid hyperplasia are independent predictors of NC-HPT, and patients with these characteristics should be monitored more closely in the postoperative period.