# Predicting Hypocalcemia and Identifying Supplementation Needs After Total Thyroidectomy: The Role of Perioperative PTH Measurements

## TL;DR

This study finds that early PTH measurements after thyroid surgery can help predict low calcium levels and guide calcium supplementation needs.

## Contribution

The study identifies preoperative calcium and 10-minute post-resection PTH as reliable predictors of hypocalcemia and supplementation needs after total thyroidectomy.

## Key findings

- Female sex, preoperative calcium, and 10-minute PTH are independent predictors of hypocalcemia at 24 hours.
- A preoperative calcium cutoff of 9.47 mg/dL and a 10-minute PTH cutoff of 24.6 pg/mL show moderate predictive accuracy.
- Early PTH measurements accurately identify patients needing calcium supplementation at 24 and 72 hours.

## Abstract

Background: Post-thyroidectomy hypocalcemia is a common complication, yet the optimal perioperative markers for identifying high-risk patients and guiding supplementation remain debated. This study aimed to evaluate factors associated with hypocalcemia at 24 h after total thyroidectomy, identify independent predictors, and assess the reliability of early PTH measurement in determining supplementation needs. Methods: We conducted a single-center prospective cohort study including 200 patients undergoing total thyroidectomy at Genesis Hospital, Thessaloniki, between November 2022 and March 2025. PTH was measured preoperatively, 10 min post-resection, and at 24 and 72 h; calcium and phosphorus were measured preoperatively and postoperatively. Results: Independent predictors of hypocalcemia at 24 h were female sex, preoperative calcium, and PTH at 10 min. Age, pathology, incidental parathyroid excision, and extent of surgery were not significantly associated with hypocalcemia. ROC analysis showed that a preoperative calcium cutoff of 9.47 mg/dL yielded an AUC of 0.73, with 70.1% sensitivity and an NPV of 82%. PTH at 10 min with a cutoff of 24.6 pg/mL yielded an AUC of 0.66, with 70.1% sensitivity and an NPV of 79%. For supplementation needs, PTH at 10 min demonstrated excellent discrimination, with a cutoff of 16.3 pg/mL at 24 h and 14.1 pg/mL at 72 h. Conclusions: Preoperative calcium and PTH measured 10 min after thyroid removal are useful markers for predicting hypocalcemia after total thyroidectomy, with early PTH also accurately identifying supplementation needs.