How is the ioPTH assay utilized in parathyroid surgery?
The half-life of PTH is 3 to 5 minutes, allowing for a rapid assay for ioPTH to be used intraoperatively to assess the functional success of the operation. This test is performed by drawing a sample of blood before the operation and 10 minutes after the suspected abnormal glands have been removed. A reduction of the ioPTH by 50% predicts successful removal of all hyperfunctioning glands, and the surgery is terminated. The rate of multiglandular disease is approximately 5% to 15% when ioPTH is used to determine the completeness of resection, whereas the rate is 10% to 35% when conventional parathyroidectomy is performed (i.e., bilateral neck exploration and removal of grossly enlarged parathyroids). Therefore, the use of ioPTH may prevent the unnecessary removal of glands that appear enlarged but are not hyperfunctional.