Accuracy of Serum Parathyroid Hormone Measured on the Early Morning of the First Postoperative Day in Predicting Clinically Significant Post-Total Thyroidectomy Hypocalcemia.

Introduction: Clinical hypocalcemia (CH) following total thyroidectomy (TT) is a potentially life-threatening condition if left untreated. This study aimed at evaluating the accuracy of parathyroid hormone (PTH) measured in the early morning of the first postoperative day (POD-1) in predicting CH, and determining the cutoff values of PTH that can predict the development of CH.

Methods: We performed a retrospective review of patients undergoing TT between February 2018 and July 2022. Serum PTH, calcium, and albumin levels were measured on morning (6-8 AM) of postoperative day one (POD-1), and serum calcium level was measured from POD-2 onwards. We performed ROC curve analysis to determine the accuracy of PTH in predicting postoperative CH, and cutoff values of PTH to predict CH.

Results: Ninety-one patients, 52 (57.1%) with benign and 39 (42.9%) with malignant goiter were included. The incidence of biochemical, and clinical hypocalcemia was 24.2% and 30.8%, respectively. In our study serum, PTH measured in the early morning of first postoperative day following TT was found to have good accuracy (AUC = .88) in predicting CH. A PTH value of ≥27.15 pg/mL was found to have a 96.4% sensitivity in ruling out CH, while a serum PTH value <10.65 pg/mL had a specificity of 95.2% in predicting CH.

Discussion: Patients with a serum PTH value of ≥27.15 pg/mL can be discharged without any supplements, those with PTH <10.65 pg/mL should be started on calcium and calcitriol supplements, while patients having PTH values between 10.65 and 27.15 pg/mL should be monitored for the development of signs and/or symptoms of hypocalcemia.