Intraoperative parathyroid hormone levels ≤40 pg/mL are associated with the lowest persistence rates after...

Intraoperative parathyroid hormone (IOPTH) monitoring is used to predict biochemical cure during parathyroidectomy for primary hyperparathyroidism; however, there is variability in the intraoperative parathyroid hormone criteria used by surgeons to predict normocalcemia after parathyroidectomy. This study sought to determine the intraoperative parathyroid hormone criteria correlated with the lowest rates of persistent hyperparathyroidism after parathyroidectomy for primary hyperparathyroidism.

This is a retrospective cohort study of 2,654 patients with primary hyperparathyroidism who underwent parathyroidectomy with intraoperative parathyroid hormone monitoring at a single institution from 1999 to 2014. Multivariate logistic regression analysis was used to measure the association between the lowest intraoperative parathyroid hormone level and the persistence of primary hyperparathyroidism after parathyroidectomy.

A total of 66 patients (2.5%) had persistent hyperparathyroidism after parathyroidectomy. Using the traditional intraoperative parathyroid hormone criteria of a ≥50% decrease from the baseline level, the rate of persistent primary hyperparathyroidism was greater when intraoperative parathyroid hormone did not decrease to ≥50% from the baseline level (17 of 180 patients [9.4%] vs 49 of 2,474 [2.0%], [OR 5.9, 95% CI 3.2-10.5, P < .001]). Regardless of whether intraoperative parathyroid hormone decreased ≥50%, patients with a lowest intraoperative parathyroid hormone above the normal range (10-65 pg/mL) had greater persistence rates compared with patients with an intraoperative parathyroid hormone <65 pg/mL (30 of 350 [8.6%] vs 36 of 2,304 [1.6%], [OR 6.6, 95% CI 3.4-12.7, P < .001]). Furthermore, patients with a lowest intraoperative parathyroid hormone 40 to 65 pg/mL had increased rates of adjusted persistence compared with patients with lowest intraoperative parathyroid hormone ≤40 pg/mL (13 of 385 [3.4%] vs 23 of 1,919 [1.2%], [OR 4.2, 95% CI 2.0-8.7, P < .001]). Patients with lowest intraoperative parathyroid hormone <5 to 20 pg/mL did not have decreased rates of persistence compared with patients with lowest intraoperative parathyroid hormone 20 to 40 pg/mL (9 of 996 [0.9%] vs 14 of 923 [1.5%], [OR 0.5, 95% CI 0.2-1.2, P = .14]).

Patients with a lowest intraoperative parathyroid hormone ≤40 pg/mL compared with the traditional criteria of a ≥50% decrease from baseline and a final parathyroid hormone in the normal range (<65 pg/mL) had the lowest rates of persistent primary hyperparathyroidism after parathyroidectomy for primary hyperparathyroidism. The single criteria of a lowest intraoperative parathyroid hormone level ≤40 pg/mL may best predict the lowest persistent disease rates after parathyroidectomy for primary hyperparathyroidism.