Prediction of permanent hypoparathyroidism by parathyroid hormone and serum calcium 24 h after thyroidectomy

Purpose: To assess the value of 24-hour intact parathyroid hormone (iPTH), serum calcium, and decreases in both were evaluated against preoperative values (iPTH and serum calcium decline) and used to determine the existence of permanent hypoparathyroidism (pHPP) after total thyroidectomy (TT). Materials and methods: The clinical data of patients who underwent total thyroidectomy in our hospital between September 2014 and July 2015 were retrospectively analyzed. Results: There were 42 cases with normal parathyroid function, 58 cases with temporary HPP, and 10 cases with pHPP. When iPTH and serum calcium were administered at 24 h after surgery, iPTH decline and calcium decline differed significantly among the three groups above (P<.01). The accuracy and positive predictive value of 24 h iPTH for pHPP were higher than any one of the others. The sensitivity, specificity, false positive rate, and accuracy were 100%, 95%, 33.33%, and 94.45%, respectively. The AUC was 0.982 when 24-hour iPTH was equal to or < 3.15 pg/mL. The use of blood calcium equal to or < 2.03 mmol/L (8.12 mg/dL) pointed to a diagnosis of pHPP, with a sensitivity of 100%, specificity of 63%, false positive rate of 78.72%, and accuracy of 66.36%. Conclusions: Measurement of the postoperative 24-h intact parathyroid hormone and serum calcium concentration can predict the occurrence of permanent hypoparathyroidism and the former is more advantageous. Postoperative 24-h intact parathyroid hormone equal to or < 3.15 pg/mL is a reliable index, and it is suitable for the prediction of postoperative permanent hypoparathyroidism.