What is the clinical significance of an elevated parathyroid hormone level after curative surgery for primary hyperparathyroidism

Objectives: Recent reports have demonstrated that between 8%-40% of patients after curative surgery for primary hyperparathyroidism (HPT) have an elevated parathyroid hormone level (ePTH). To determine the clinical significance of ePTH and if it is a potential risk factor for recurrent HPT, we reviewed our experience. Methods: 611 consecutive patients underwent curative parathyroidectomy for primary HPT by one surgeon. Patients with ePTH [defined as postoperative parathyroid hormone (PTH) levels ≥65 pg/mL at least 1 week after surgery with normal calcium levels] were compared with those with normal PTH. Results: ePTH occurred in 111/611 (18.2%) patients. When compared with those with normal PTH, ePTH patients were older and had higher preoperative PTH and alkaline phosphatase levels (P < 0.05). Importantly, recurrent HPT was significantly higher in patients with ePTH (5.4% versus 1.2%, P < 0.05). Further analysis of the ePTH patients revealed that serum calcium 1-week after surgery was predictive of recurrent HPT. In ePTH patients with postoperative calcium ≥9.7 mg/dL, the recurrence rate was 16% compared with 0% in those whose calcium was <9.7 mg/dL. Conclusions: Most of patients (95%) with ePTH after curative parathyroidectomy for primary HPT will not develop recurrent HPT. However, recurrent disease is significantly more common among patients with ePTH and was always associated with postoperative calcium ≥9.7 mg/dL. Thus, these data suggest that streamlining postoperative surveillance to this subset of patients may optimize resource utilization.