How should we define cure after parathyroidectomy for normocalcemic primary hyperparathyroidism? A retrospective cohort study.

Cure after surgery for normocalcemic primary hyperparathyroidism (NHPT) is defined as parathyroid hormone (PTH) normalization. However, an increase of PTH is frequently observed in cured patients with hypercalcemic primary hyperparathyroidism (HHPT). Therefore, this criterion must be redefined. A single-center retrospective study was performed including all patients who underwent surgery for Primary Hyperparathyroidism from 2013 to 2019. Cure rates of different types of hyperparathyroidism were analyzed. PTH reduction was studied as a possible criterion to define cure in patients with NHPT. One-hundred and eighty-six patients were included: 173 with HHPT and 13 with NHPT. After a mean follow-up of 33.4 months, 174 (93.6%) patients were considered cured. Cure was more frequent in the group of patients with HHPT (97.1% vs. 46.2%, p < 0.001). In the multivariate analysis, surgical failure was associated with NHPT and multiglandular disease. Forty-nine (30.1%) cured patients with HHPT had an increased PTH during the follow-up. When decline of PTH levels was studied in patients with HHPT to define cure, the area under curve was 0.92. A cut-off value of 40% in PTH reduction achieved a sensitivity and specificity of 83.4% and 80.0%. If cure was defined as a 40% reduction of PTH, cure rate in the group of patients with NHPT would increase to 69.2%. Patients with NHPT had a lower cure rate than patients with HHPT. A significant number of cured patients with HHPT had an increased PTH during follow-up. A 40% reduction in PTH levels is proposed as an alternative definition for cure in patients with NHPT.