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

Area of Science:

• Endocrinology
• Surgical Oncology
• Biochemistry

Background:

• Intraoperative parathyroid hormone (IOPTH) monitoring aids minimally invasive parathyroidectomy for primary hyperparathyroidism (pHPT).
• Existing IOPTH protocols for biochemical cure prediction may be affected by extremely high baseline IOPTH levels (>500 pg/mL).

Purpose of the Study:

• To investigate clinical differences in patients with extremely elevated baseline IOPTH (>500 pg/mL).
• To determine the most appropriate IOPTH monitoring protocols for patients with extremely high baseline IOPTH levels.

Main Methods:

• Retrospective review of 237 patients undergoing parathyroidectomy for pHPT with IOPTH monitoring (2016-2020).
• Baseline IOPTH levels categorized as 'elevated' (>65-500 pg/mL) and 'extremely elevated' (>500 pg/mL).
• Analysis of final IOPTH levels, >50% decrease from baseline, normal IOPTH achievement, and 6-week postoperative calcium levels.

Main Results:

• 24% of patients had extremely elevated baseline IOPTH (>500 pg/mL).
• Extremely elevated baseline IOPTH was associated with higher final IOPTH levels and less likelihood of reaching normal range (P=0.019).
• Despite differences in final IOPTH, >50% decrease from baseline was equally likely, and 6-week postoperative calcium levels did not differ between groups.

Conclusions:

• Extremely elevated baseline IOPTH (>500 pg/mL) is not uncommon in pHPT surgery.
• While final IOPTH may remain higher, biochemical cure rates are comparable, suggesting current stringent IOPTH criteria may not be suitable for this patient subgroup.