Intraoperative Parathyroid Hormone Kinetics are Variable: An In-Vivo Analysis

Objectives: Intraoperative parathyroid hormone (IOPTH) monitoring has become routine in parathyroid surgery to facilitate less invasive techniques to treat hyperparathyroidism. Despite this, little is known about in vivo IOPTH kinetics, which can greatly affect the reliability of its interpretation. Methods: A prospective cohort of patients undergoing routine parathyroidectomy was studied. During each case, IOPTH was measured frequently, during all key perioperative events. Qualitative, univariate, and multivariate analysis was performed to better understand the patterns of in vivo IOPTH kinetics. Results: The IOPTH increased from preoperative baseline in every case, but some patients had a rapid spike after gland manipulation while others had a more gradual increase. The IOPTH peak occurred prior to excision in almost every case. The IOPTH began to fall prior to excision, typically returning to preoperative baseline levels just before excision. The average in vivo half-life of parathyroid hormone (PTH) was 5.2 minutes. Conclusion: There is substantial variation in the in vivo IOPTH kinetics and more research is needed to understand predictors of kinetic patterns and PTH half-life during parathyroidectomy.