Background: It is unclear when intraoperative intact parathyroid hormone (IOPTH) measurement should be performed, and there is also some uncertainty about the best cutoff point to use in predicting the success of parathyroidectomy in renal hyperparathyroidism.
Objective: To determine the cutoff values for IOPTH, both for parathyroid levels and for postoperative timing after parathyroidectomy in order to compare successful parathyroidectomy with persistent hyperparathyroidism in renal hyperparathyroidism.
Material and Method: This was a retrospective study of 85 patients who underwent total parathyroidectomy with autotransplantation in the Head and Neck Surgery Department in Rajavithi Hospital between October 1st 2014 and September 30th 2016. IOPTH levels were measured preoperatively at IOPTH 0 minutes, and at 10-minute intervals after successful parathyroidectomy for a duration of 1 hour (IOPTH at 10, 20, 30, 40, 50 and 60 minutes) with iPTH level on day 3 (72 hours after surgery) below 65 pg/ml taken as a predictor of successful treatment of renal hyperparathyroidism.
Results: Fifty-eight patients (68.2%) had successful treatment according to the above criteria. The ROC values of the decrement of IOPTH levels at 10, 20, 30 and 40 minutes were 0.644, 0.767, 0.799, and 0.809 respectively. In all patients that were successfully treated, the decrement of IOPTH was more than 80%, while all patients whose treatment was unsuccessful had an IOPTH decrement of less than 70%. An IOPTH level decrement of between 70 and 80% 20 minutes postoperatively had a sensitivity of 82.1 to 96.4%, while a decrement of IOPTH level of more than 90% after 20 minutes yielded 100% specificity for successful treatment of renal hyperparathyroidism.
Conclusion: The cutoff point for IOPTH time at 20 minutes with at least a 80% decrement yields a sensitivity of 82.1% for predicting successful surgery, while more than 90% decrement in IOPTH levels has 100% specificity for predicting successful treatment.

Keywords: Intraoperative, Intact parathyroid hormone, Hyperparathyroidism and chronic renal failure