Intraoperative parathyroid hormone monitoring fails to detect double parathyroid adenomas: A 2-institution experience

Background. We hypothesized that intraoperative parathyroid hormone monitoring (IOPTH) reliably would detect double parathyroid adenomas. Methods. This was a retrospective study of 20 patients undergoing conventional parathyroidectomy with resection of exactly 2 abnormal glands. Full exploration was performed regardless of IOPTH values, which were measured after anesthetic induction and 5 and 10 minutes following removal of the first abnormal parathyroid gland. Failure to fall below 50 % of baseline value by 10 minutes following resection of the first gland indicated the presence of multiglandular disease. Results. All patients were cured. All excised glands were hypercellular on histolog. Mean IOPTH values in 9 of the 20 patients with true negative results (noncurative decrease, another gland present) were 66 % +/- 7 % of 5 minutes and 83 % +/- 15 % at 10 minutes. The IOPTH values in 11 of the 20 patients with false positive results (curative decrease, another gland present) were 28 % +/- 4 % at 5 minutes and 18 % +/- 2 % at 10 minutes. The false positive rate of IOPTH was 55 %. Conclusions. We found that IOPTH failed to reliably detect the presence of double parathyroid adenomas. These data suggest that caution should be exercised when terminating limited parathyroid exploration based on a curative fall in IOPTH values.