Use of Intraoperative Parathyroid Hormone Assay

Abstract

Although there remain situations when conventional bilateral parathyroid exploration is the operation of choice for primary hyperparathyroidism, focused, single-gland exploration (minimally invasive parathyroidectomy [MIP]) has become the standard operation for most patients. Successful surgery requires accurate preoperative imaging and measurement of PTH intraoperatively (IOPTH).

IOPTH is measured prior to the beginning of anesthesia, at the time the adenoma is removed and at varying time intervals thereafter. Failure to measure IOPTH at the time of excision of the adenoma can result in failure to detect a spike in IOPTH and result in incorrect interpretation of subsequent values. Decrease of IOPTH of at least 50 % from baseline and into the normal range or to an absolute level of <40 pg/ml is indicative of successful surgery. This algorithm works even if the baseline PTH is in the normal range.

In some patients, bilateral exploration identifies enlarged, hypercellular parathyroids when the IOPTH decrease appears adequate. The clinical significance of this is uncertain. The significance of persistently elevated PTH postoperatively in patients who have successful parathyroidectomy with a decrease of calcium into the normal range also is uncertain. The performance of MIP without an adjunct assessment of the adequacy of surgery, whether IOPTH or the use of a gamma probe, can result in a higher failure rate. IOPTH is also useful when bilateral parathyroid exploration or reoperative surgery for persistent hyperparathyroidism is performed.