Intraoperative parathyroid hormone monitoring in patients with recognized multiglandular primary hyperparathyroidism

Intraoperative parathyroid hormone (IOPTH) monitoring reliably predicts cure of primary hyperparathyroidism (PHPT) due to single-gland disease. However, its utility in PHPT caused by multiple-gland disease (MGD) is still debated, for both detection and prediction of adequate resection. Our hypothesis is that once MGD is encountered during an operation, more stringent criteria for determining adequate resection can improve cure rates.

This was a retrospective cohort study of patients with PHPT who were found to have MGD during the course of focused parathyroidectomy. IOPTH levels after completed multiple parathyroid gland excision were compared between cured patients and those with persistent hyperparathyroidism.

Of 1855 patients undergoing focused parathyroidectomy, 243 were found to have MGD. Of the 207 study patients with MGD, 193 were cured and 14 had persistent hyperparathyroidism. After final gland excision, the mean±SEM percentage decrease in IOPTH from the baseline was of significantly greater magnitude for the cured group (90.0±0.5%) than for the persistent group (74.0±3.8%) (p<0.01). The mean±SEM IOPTH after completed multigland excision was higher in the persistent group (44.0±8.4 pg/ml) than in the cured group (34.0±3.5 pg/ml) (p=0.19), although both were within the normal range (12-65 pg/ml). When the groups were analyzed for an incremental fall of IOPTH from the baseline, the criteria of ≥75% drop and into the normal range improved the positive predictive value from 93.2 to 96.6% when compared to the standard criterion of a 50% decrease from the baseline.

When PHPT due to MGD is recognized and focused parathyroidectomy is extended, a final postexcision PTH level that is ≥75% decreased from the baseline PTH level and in the normal range should be used to predict adequate gland resection.