Justified follow-up: a final intraoperative parathyroid hormone (ioPTH) Over 40 pg/mL is associated with an increased risk of persistence and recurrence in primary hyperparathyroidism.

Introduction: After parathyroidectomy for sporadic primary hyperparathyroidism (PHPT), overall rates of persistence/recurrence are extremely low. A marker of increased risk for persistence/recurrence is needed. We hypothesized that final intraoperative parathyroid hormone (FioPTH) ≥40 pg/mL is indicative of increased risk for disease persistence/recurrence, and can be used to selectively determine the degree of follow-up.

Method: A retrospective review of PHPT patients undergoing parathyroidectomy with ioPTH monitoring was performed. An ioPTH decline of 50 % was the only criteria for operation termination. Patients were grouped based on FioPTH of <40, 40-59, and >60 pg/mL.

Results: Between 2001 and 2012, 1,371 patients were included. Mean age was 61 ± 0.4 years, and 78°% were female. Overall persistence rate was 1.4°%, with a 2.9°% recurrence rate. Overall, 976 (71°%) patients had FioPTH < 40, 228 (16.6°%) had FioPTH 40-59, and 167 (12.2°%) had FioPTH ≥60. Mean follow-up was 21 ± 0.6 months. Patients with FioPTH <40 were younger, with lower preoperative serum calcium, PTH, and creatinine (all p ≤ 0.001). Patients with FioPTH <40 had the lowest persistence rate (0.2 %) versus patients with FioPTH 40-59 (3.5 %) or FioPTH ≥60 (5.4 %; p < 0.001). Recurrence rate was also lowest in patients with FioPTH <40 (1.3 vs. 5.9 vs. 8.2 %, respectively; p < 0.001). Disease-free status was greatest in patients with FioPTH <40 at 2 years (98.5 vs. 96.8 vs. 90.5 %, respectively) and 5 years (95.7 vs. 72.3 vs. 74.8 %, respectively; p < 0.01).

Conclusions: Patients with FioPTH < 40 pg/mL had lower rates of persistence and recurrence, than patients with FioPTH 40-59, or ≥60. Differences became more apparent after 2 years of follow-up. Patients with FioPTH ≥40 pg/mL warrant close and prolonged follow-up.