Background: Surgical resection is the only curative therapy for patients with primary hyperparathyroidism (1HPT). Although cure rates of parathyroidectomy are generally high, failure is most often due to unrecognized multigland disease (MGD), which compromises 15-20% of patients with 1HPT. The use of intraoperative PTH (ioPTH) monitoring is well established for single-gland disease. Controversy remains over the utility of ioPTH in MGD, with concern for false-positive results leading to prematurely concluding the operation and leaving behind abnormal parathyroid tissue, risking future recurrence. The aim of this study was to determine the utility of ioPTH monitoring for MGD.
Methods: Between November 2000 and March 2008, data were prospectively collected on 755 patients with 1HPT who underwent parathyroidectomy. PTH samples were collected pre-incision, and then at 5, 10, and 15 min after excision of suspected abnormal parathyroid gland(s). Surgical cure was defined as a drop of greater than 50% in PTH level. Patients were clinically cured if they became normocalcemic postoperatively and remained so for 6 months. The data were analyzed to determine how accurately ioPTH predicted success or failure of parathyroidectomy.
Results: Of the 755 patients, 163 (21.5%) were found to have MGD on pathology. Intraoperative PTH monitoring was used in 161 of these cases. In 146/161 cases (90.7%), the ioPTH level fell by at least 50% after removal of all suspected abnormal glands. All of these patients (100%) remained normocalcemic postoperatively. In 15/161 cases (9.3%), the PTH level did not fall by >50%. For 11/15 cases (73%), patients remained hypercalcemic postoperatively or had recurrence. However, in the remaining four cases, the patients became normocalcemic postoperatively despite failure of the PTH to fall by >50%. In each of these patients, PTH levels fell by 40-50%.
Conclusions: ioPTH monitoring accurately predicted success or failure of parathyroidectomy in 97.5% (157/161) of patients with MGD. A fall of ioPTH by >50% can be used as a highly accurate predictor of cure in patients with MGD. Therefore, ioPTH monitoring is a very useful tool in patients with 1HPT and MGD.