Background: The correct interpretation of intraoperative parathyroid hormone (IOPTH) levels in patients with primary hyperparathyroid patients (pHPT) with multiglandular disease (MGD) can impact the success rate of initial parathyroid exploration, but it remains an understudied topic. Methods: In all, 592 of 823 patients were explored by a single surgeon with biochemical evidence of pHPT (1997-2007) and underwent parathyroidectomy using IOPTH. We investigated the incidence of MGD in patients with an appreciable (>50%) decrease in IOPTH levels and in patients whose levels failed to normalize after single gland excision. Results: The mean age of patients was 56.7 years, and 74% of patients were women. Thirty-one patients had PTH levels that decreased by greater than 50% from baseline 10-15 min after single gland excision, but the levels failed to normalize. Of these, 9 patients (29%) had MGD (8 double adenomas, 1 hyperplasia). The incidence of MGD in the remainder of IOPTH patients was 13.9% (78 of 561 patients). Within the subgroup of 31 patients, those with single adenomas did not differ from patients with MGD in baseline IOPTH levels and weights of first adenoma excised, although they demonstrated greater serum creatinine concentrations and a decrease in mean IOPTH. Conclusion: Commonly accepted decreases in IOPTH levels (>50%) for patients who undergo minimally invasive parathyroidectomy may lead to an appreciable number of missed parathyroid adenomas or hyperplastic disease.
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