Management of Postthyroidectomy Hypocalcemia Using Intraoperative Parathyroid Hormone Monitoring

Importance Postthyroidectomy hypoparathyroidism is typically diagnosed with low serum calcium levels, often requiring patients to remain in the hospital for appropriate treatment. Given the short half-life of parathyroid hormone (PTH), can hypoparathyroidism be diagnosed intraoperatively when re-exploration and autotransplant are still possible? Objective To determine whether intraoperative parathyroid hormone monitoring (ioPTH) permits the stratification of patients into appropriate tiers for postoperative supplementation. Design, Setting, and Participants This retrospective cohort study included patients undergoing total or completion thyroidectomy and was conducted at a single academic center from January 2021 and December 2022. Analysis was completed in July 2024. To complete the planned threshold analysis, additional patients who had surgery between January 2020 to December 2020 and January 2023 to June 2023 and were discharged with calcium carbonate and calcitriol supplementation were included. Patients undergoing concomitant parathyroidectomy or lateral neck dissection were excluded. Exposures All patients had a baseline PTH level drawn in the preoperative area. Additional ioPTH levels were drawn immediately and 10 minutes after thyroid excision. The exposure of interest was the absolute and relative change from baseline to immediate and 10-minute ioPTH. Main Outcomes and Measures Outcome groups were determined by supplementation tier. A control group that received no supplementation was compared with the groups that received calcium carbonate only or calcium carbonate plus calcitriol. Logistic regression models were used to analyze the threshold at which ioPTH could predict postoperative supplementation tier. Results Of the 217 patients included (mean SD age, 49.94 15.56 years; 193 female individuals 89%; 15 patients 7% were Black, and 197 patients 91% were White), 100 (46.1%) received no supplementation, 61 (28.1%) received calcium carbonate, and 56 (25.8%) received calcium carbonate plus calcitriol. Ninety eight (45.2%) experienced temporary hypoparathyroidism, while 2 patients developed permanent hypoparathyroidism. The best model to predict any postoperative supplementation used a 30% decrease from baseline to immediate ioPTH with an overall accuracy rate of 78.20% (sensitivity, 74.78%; specificity, 82.29%). The best model to predict use of calcium carbonate plus calcitriol supplementation corresponded to an immediate ioPTH level of 22 pg/mL, with an overall accuracy rate of 73.91% (sensitivity, 70.00%; specificity, 78.18%). Conclusions and Relevance The results of the threshold analysis demonstrated the utility of ioPTH in guiding postoperative supplementation. ioPTH may also be a useful adjunct in guiding parathyroid autotransplant intraoperatively, potentially reducing the risk of permanent hypoparathyroidism.