Intraoperative parathyroid hormone testing: what have we learned?

Objectives/hypothesis: The development of rapid, sensitive assays for measuring the intact parathyroid hormone (iPTH) molecule has the potential to allow the surgeon to determine the success of parathyroid surgery intraoperatively. The purpose of the study was to review our results in the context of currently held beliefs regarding the ability of the intraoperative iPTH to predict resolution of hyperparathyroidism.

Study Design: Retrospective review.

Methods: The study series is a retrospective review of 107 consecutive parathyroidectomies performed by a single surgeon. Patients with primary, secondary, and tertiary hyperparathyroidism were included.

Results: The intraoperative assay allowed an overall success rate of 93.4% across all patient categories. The success rate in patients with primary hyperparathyroidism was 95.7%. Measuring the iPTH level at 10 versus 15 minutes after the removal of tissue did not significantly affect the predictive value of the test. A decrease of 50% in the iPTH level after the resection of hyperfunctioning tissue was prognostic of successful treatment of the hyperparathyroid state. By contrast, a postexcision iPTH level that was within the normal range was not always predictive of cure.

Conclusions: The intraoperative iPTH assay is particularly useful in the treatment of primary hyperparathyroidism. The assay eliminates the need for intraoperative frozen-section analysis in most cases and allows the surgeon to perform limited resections with confidence. This is especially true in complicated parathyroid surgeries, such as revision surgeries or those requiring concomitant thyroid surgery. The assay is also useful in secondary hyperparathyroidism, although it appears that the inability to identify small nonfunctional or hypofunctional supernumerary parathyroid glands means that long-term normocalcemia may not be assured.