A Study On The Decline Rate Of Intraoperative Parathyroid Hormone In Evaluating The Prognosis Of Hypocalcemia After Total Thyroidectomy

Objective:The aim of this study was to explore the accuracy of PTH decline rate(△PTH%)in predicting postoperative hypocalcemia in patients with total thyroidectomy,to calculate the cutoff value of △PTH% that predicts the hypocalcemia,transient and permanent hypoparathyroidism after total thyroidectomy,and to determine whether the postoperative PTH recovery time could be predicted based on △PTH%.Methods:This is a retrospective study.We selected 164 patients who underwent total thyroidectomy with or without neck dissection from October 2018 to October 2019 in our department by one surgeon.The following data include the patient’s age,gender,body mass index(BMI),surgical method,whether it is accompanied by Hashimoto’s thyroiditis,the number of central neck dissection and metastases were collected before the surgery.Laboratory data such as serum total calcium,vitamin D level,serum PTH and albumin levels before surgery,intraoperative PTH levels measured after 15 minutes and postoperative lowest calcium during the postoperative hospitalization were recorded.Then calculate △PTH%[△PTH%=(preoperative PTHintraoperative PTH)/preoperative PTH×100%].At the same time,we need to record the daily intravenous and oral calcium supplementation during hospitalization and calculate the average value.After discharge the serum PTH and calcium levels were followed up at 1 month,2-3 months and 4-6 months.Finally,we analyzed the incidence of hypocalcemia,transient and permanent hypoparathyroidism;the correlation between △PTH% and hypocalcemia and hypoparathyroidism;the cutoff value of △PTH% and PTH to predict hypocalcemia and hypoparathyroidism;the PTH recovery time and cutoff value.The collected data will be analyzed by IBM SPSS Statistics(?) version 25.0.(1)Receiver operating characteristic(ROC)curve was used to analyzed the cutoff value of IOPTH and △PTH% respectively to predict postoperative hypocalcemia,transient and permanent hypoparathyroidism.According to the area under the curve(AUC),comparing the diagnostic efficiency.(2)SPSS 25.0 software was used to perform independent sample T test for continuous numerical variables and single-factor Chi-square Test for categorical variables,so as to screen out the variable factors with statistical differences,then carry out Binary Logistic regression analysis on these variables and get the independent risk factors of hypocalcemia,transient and permanent hypoparathyroidism.P<0.05 was used as the standard for statistically significant differences.Results:(1)Of the 164 patients,37(23%)had only IOPTH less than 15pg/ml,13(8%)had only hypocalcemia,46 had both hypocalcemia and IOPTH(28%)less than15pg/ml,68 cases(41%)had normal calcium and IOPTH.The incidence of hypocalcemia during hospitalization was 36%(59/164),transient hypoparathyroidism was12.8%(21/164)and the permanent hypoparathyroidism was 2.4%.(4/164).(2)After ROC curve analysis,the cutoff value of △PTH% for predicting hypocalcemia after total thyroidectomy was 64.59%(AUC=0.716,P<0.001),and the cutoff value of IOPTH was 14.24pg/ml(AUC= 0.707,P<0.001).The cutoff value of△PTH% for predicting transient hypoparathyroidism after surgery was 60.36%(AUC=0.664,P=0.015),and the cutoff value of IOPTH was 12.32pg/ml(AUC=0.678,P=0.009).The cutoff value of △PTH% for predicting permanent hypoparathyroidism after surgery is 74.96%(AUC=0.806,P=0.037),and the cutoff value of IOPTH is7.59pg/ml(AUC=0.882,P=0.009).(3)The variable factor of △PTH%(OR:17.425;CI:4.281~70.927;P<0.001)is the independent risk factor for hypocalcemia during hospitalization.Age(OR:0.943;CI:0.899~0.988;P=0.015),IOPTH(OR:0.934;CI:0.885~0.986;P=0.013),△PTH%(OR: 22.004;CI: 2.055~235.643;P=0.011)are independent risk factors for transient hypoparathyroidism.(4)A total of 83 patients had IOPTH less than 15pg/ml.65(78.3%),8(9.6%),and 6(7.2%)who recovered respectively within 1 month,2 to 3 months,and4 to 6 months,4 cases(4.8%)did not recover within 6 months.Conclusion:(1)△PTH% was effectively to predict the risk of hypocalcemia,transient and permanent hypoparathyroidism after total thyroidectomy.(2)When △PTH%≥64.59%,it can predict the incidence of hypocalcemia and provide guidance to clinicians on effective and appropriate calcium supplementation.(3)△PTH% may provide a new evaluation system for individualized strategy treatment programs and realize the effective and economical treatment.