Extreme Elevation of Baseline Intraoperative Parathyroid Hormone Measurements: Should Usual Protocols Apply?

Introduction: Intraoperative parathyroid hormone (IOPTH) monitoring is routinely used to facilitate minimally invasive parathyroidectomy. Many IOPTH protocols exist for predicting biochemical cure. Some patients are found to have extremely high baseline IOPTH levels (defined in this study as >500 pg/mL), which may affect the likelihood of satisfying certain final IOPTH criteria. We aimed to discover whether clinically significant differences exist in patients with extremely high baseline IOPTH and which IOPTH protocols are most appropriately applied to these patients.Materials and methods: This is a retrospective review of 237 patients who underwent para-thyroidectomy with IOPTH monitoring for primary hyperparathyroidism (pHPT) from 2016 to 2020. Baseline IOPTH levels, drawn prior to manipulation of parathyroid glands, were grouped into categories labeled elevated (>65-500 pg/mL) and extremely elevated (>500 pg/mL). Final IOPTH levels were analyzed to determine whether there was a >50% decrease from baseline and whether a normal IOPTH value was achieved. 6-wk postoperative cal-cium levels were also examined.Results: Of the patients in this cohort, 76% were in the elevated group and 24% in the extremely elevated group. Male sex and higher preoperative PTH levels were correlated with higher baseline IOPTH levels. Patients with extremely elevated baseline IOPTH were less likely to have IOPTH fall into normal range at the conclusion of the case (P = 0.019), and final IOPTH levels were higher (P < 0.001), but the IOPTH was equally likely to decrease >50% from baseline. There was no difference in the mean post-operative calcium levels between the two groups at 6-wk or at longer term follow-up (mean 525 d).Conclusions: Detection of baseline IOPTH levels >500 pg/mL during parathyroidectomy performed for pHPT is not uncommon. IOPTH in patients with extremely elevated baseline levels were less likely to fall into normal range, but follow-up calcium levels were equal,suggesting that applying more stringent IOPTH criteria for predicting biochemical cure may not be appropriate for this population.(c) 2022 Elsevier Inc. All rights reserved.

Automated summary

This study investigates whether there are clinically significant differences in patients with extremely high baseline IOPTH and which IOPTH protocols are most appropriate for them. The results show that patients with extremely elevated baseline IOPTH are less likely to reach normal IOPTH levels, but postoperative calcium levels are comparable. Therefore, applying stricter IOPTH criteria for predicting biochemical cure may not be suitable for this population.