A rising ioPTH level immediately after parathyroid resection: are additional hyperfunctioning glands always present? An application of the Wisconsin Criteria

Abstract

Objective: This study was designed to determine if a rising intraoperative parathyroid hormone (ioPTH) level following parathyroid resection indicates multiple hyperfunctioning glands and to determine the appropriate intraoperative management.

Summary background data: IoPTH monitoring is commonly used to guide parathyroid surgery. A significant rise in the ioPTH immediately after resection of a single parathyroid is often perceived to be indicative of the presence of additional hyperfunctioning glands.

Methods: A total of 797 consecutive patients underwent parathyroidectomy for primary hyperparathyroidism with ioPTH monitoring. Patients with an elevated 5 minute ioPTH were extensively studied. Operative success was defined as normocalcemia 6 months after surgery.

Results: Of the 797 patients, 108 (14%) had a rising ioPTH 5 minutes after resection of a single parathyroid. Of these 108 patients, 36 (33%) continued to have elevated ioPTH levels and further exploration revealed additional hyperfunctioning glands. Importantly, in the majority of patients (n = 72 or 67%), the ioPTH started to fall after an additional 5 minutes (10 minutes after resection). The ioPTH declined by more than 50% from the 5 minute elevated value in 30%, 89%, and 99% of patients at 10, 15, and 20 minutes after resection, respectively. Importantly, this fall correctly predicted operative success in 100% of patients after removal of a single abnormal gland.

Conclusions: A rising ioPTH level immediately after parathyroidectomy is observed in 14% of patients. The majority of these patients do not have additional hyperfunctioning glands. Most of patients fell below 50% of the 5 minute elevated value within 20 minutes of gland resection and in all cases this fall correctly predicted operative success.

Figure 1

The elevated 5 minute ioPTH value can be used as a new baseline to discriminate between patients with a single and multiple abnormal parathyroid glands. Patients with a single abnormal gland and a rising 5 minute ioPTH rapidly fall below 50% of this elevated value, though not 50% of the pre-incision value (A). In contrast, patients with multiple abnormal glands do not decline below 50% of the elevated 5 minute newly set ioPTH threshold (B). Data is plotted a mean ± SEM.

Figure 2

Patients with a single abnormal gland rapidly fall below a threshold defined as 50% of the elevated 5 minute ioPTH. If the elevated 5 minute ioPTH value is defined as the new baseline, a 50% decline from this point may be used to discriminate between single and multiple gland disease. Patients with only a single abnormal gland fall rapidly below this threshold.