Assessing the impact of low baseline parathyroid hormone levels on surgical treatment of primary hyperparathyroidism.

Objectives/hypothesis: To compare patients with a parathyroid hormone index (iPTH) level less than 100 pg/mL (low baseline) with patients with an index level greater than 100 pg/mL (high baseline) relative to intraoperative iPTH levels (IOPTH), surgical findings, imaging, and outcome.

Study Design: Retrospective chart review.

Methods: : The medical records of 284 patients with primary hyperparathyroidism undergoing parathyroid exploration utilizing IOPTH were reviewed. One hundred fifty-eight patients with a low baseline iPTH level were compared with 144 patients with a high baseline iPTH level. Patients were correlated in regard to IOPTH results, surgical findings, preoperative localization imaging, and surgical outcome.

Results: There was no significant difference between the two groups in regard to recalcitrant disease. Twenty percent of the low baseline group of patients had multigland disease, versus 8% of the high baseline patients. The kinetic profile of iPTH degradation differed between the two groups, with the low baseline group demonstrating a significantly lower percentage drop compared to the high baseline group.

Conclusions: Patients with preoperative low baseline iPTH levels are over two times more likely to have multigland disease than patients with high baseline levels. Preoperative imaging in this group appears to be less likely to yield a solitary adenoma, even in the absence of multigland disease. IOPTH degradation kinetics is variable between groups, resulting in the possibility of inconsistent correlation with complete resection. These findings suggest that the current IOPTH guidelines, with reference to adequacy of resection, may need to be amended, especially for patients with low baseline iPTH levels. Laryngoscope, 2009.