Persistent elevation of parathyroid hormone after curative parathyroidectomy: A risk factor for recurrent hyperparathyroidism.

Background: Up to 45% of patients may have persistently elevated parathyroid hormone (PTH) levels after curative parathyroidectomy for primary hyperparathyroidism (PHPT), although the clinical significance is unclear. We aimed to assess the long-term clinical significance of persistently elevated PTH early after parathyroidectomy.

Methods: A prospectively collected institutional database was queried for patients who underwent parathyroidectomy for sporadic PHPT between 12/99 and 6/22 and had normal serum calcium levels at 6 months postoperatively. Demographic and clinical data were collected, including diagnoses associated with secondary HPT (gastrointestinal malabsorptive diseases, kidney disease, and vitamin D deficiency). Patients were divided into two groups: normal PTH or elevated PTH at 6 months postoperatively. The rate of persistently elevated PTH, average time to PTH normalization, and time to recurrence were determined.

Results: The final cohort included 1146 patients; 849 (91%) had normal PTH levels and 194 (17%) had early postoperative normocalcemia with elevated PTH at 6 months postoperatively. Among 194 patients (mean follow-up: 50 ± 53 months), 14 (7.2%) developed recurrent pHPT and 86 (44.3%) had normalization of PTH levels (median time to normalization: 12 months) (IQR: 9 and 15). There was no difference in the presence of diagnoses associated with secondary HPT between patients who had recurrent PHPT, normalization of PTH levels, or remained normocalcemic with persistently elevated PTH levels. The median time to recurrence was 22 months (IQR: 11 and 48) for the 7.2% of patients who developed recurrent PHPT compared to 2.4% in the 849 patients with normal calcium and PTH levels at 6 months (p < 0.001).

Conclusions: Following curative parathyroidectomy, persistent elevation of PTH levels is not uncommon. Although most patients have a durable cure, it may be an early sign of persistent/recurrent PHPT. Long-term surveillance for recurrence is necessary.