Parathyroidectomy Outcomes in Normohormonal Primary Hyperparathyroidism and the Miami Criterion

Introduction: Patients with normohormonal hyperparathyroidism (NHpHPT) pose a difficulty for endocrine surgeons given the lack of management and surgical guidelines. Our aim was to report our classic primary hyperparathyroidism (CpHPT) and NHpHPT surgical experience, as well as analyze the diagnostic performance of the Miami Criteria in these cohorts, to better guide clinical practice in disease management.

Methods: Patients diagnosed with CpHPT (PTH >65 pg/dL) and NHpHPT (15-65 pg/dL) who underwent parathyroidectomy at a single center were identified. All patients had calcium levels >10.5 pg/dL preoperatively. The NHpHPT group was further subdivided based on preoperative PTH levels, including an ‘upper normal’ cohort (51-65 pg/dL) and a ‘lower normal’ cohort (15-51 pg/dL). Preoperative, intraoperative (including IOPTH), and postoperative data were collected and statistically compared.

Results: A total of 165 patients with CpHPT and 31 patients with NHpHPT were identified. Cure rates (defined as normocalcemia at 6 months postop) were similar at 95.76% and 87.1% in the CpHPT and NHpHPT groups, respectively (p = 0.0546). Cure rates were similar between ‘upper normal’ NHpHPT patients (94.12%) and ‘lower normal’ NHpHPT patients (78.57%; p = 0.1988), though the latter cohort tended to have lower cure rates. The rates of cure in those who demonstrated ≥ 50% drop within 10 minutes of surgical resection differed between the CpHPT cohort (97.42%) and the NHpHPT cohort (93.55%, p = 0.0449). The rate of cure in Miami criterion fulfilling ‘upper normal’ NHpHPT patients was 100% but only 71.42% in the ‘lower normal’ NHpHPT cohort (p = 0.0424).

Conclusions: In patients with NHpHPT, intraoperative parathyroid hormone declines of ≥ 50% were predictive of postoperative cure and surgery should be considered as an important means of definitive treatment among patients with PTH level between 56-65 pg/mL. However, NHpHPT patients with lower normal preoperative levels experience a lower curative surgery when fulfilling the Miami criterion. Further research is warranted for these patients regarding management.