Normocalcemic parathormone elevation after successful parathyroidectomy: Long-term analysis of parathormone variations over 10 years

Background: The long-term significance of normocalcemic parathormone elevation (NPE) after successful parathyroidectomy for sporadic primary hyperparathyroidism remains unclear. Method: Of 239 consecutive patients who underwent targeted parathyroidectomy with intraoperative parathormone monitoring, 96 were followed for ≥10 years. NPE was defined as a normal serum calcium level and parathormone (PTH) above the normal reference range ≥6 months after successful parathyroidectomy. Recurrence was defined as elevated serum calcium and PTH levels ≥6 months after parathyroidectomy. Risk factors for NPE, patterns of postoperative PTH variation, and 10-year outcomes were analyzed. Results: Of 96 patients followed ≥10 years, 42 had postoperative NPE. Only male gender (P =.008) was a risk factor for NPE, and NPE did not predict recurrence. Three patterns of postoperative NPE were identified in patients with ≥3 PTH measurements over this 10-year period. Group 1 (n = 11): 1 to 2 consecutive PTH elevations; none recurred, and most were explained by physiologic variation. Group 2 (n = 23): multiple PTH fluctuations; 3 recurred, and almost all had physiologic variations. Group 3 (n = 4): PTH always elevated; 2 recurred. Conclusion: Postoperative NPE may be a dynamic, reversible, and transient clinical entity that does not predict recurrence. Nevertheless, patients with postoperative NPE should be monitored and an attempt made to correct any obvious potential causes of PTH elevation.