Hypercalcemia with a parathyroid hormone level of ≤50 pg/mL: Is this primary hyperparathyroidism?

Primary hyperparathyroidism is characterized by hypercalcemia with inappropriately normal or elevated parathyroid hormone. However, the absolute parathyroid hormone value that is defined as inappropriately normal is unclear. We reviewed our experience with parathyroidectomy in patients with hypercalcemia and parathyroid hormone of ≤50.0 pg/mL (normal range 12.0-88.0 pg/mL).

A total of 2,349 patients underwent parathyroidectomy for primary hyperparathyroidism between 2000 and 2021. Of these, 149 patients had preoperative parathyroid hormone ≤50.0 pg/mL (parathyroid hormone ≤50). The biology and outcomes were compared to patients with parathyroid hormone >50.0 pg/mL (parathyroid hormone >50).

Of the parathyroid hormone ≤50 patients, the median parathyroid hormone was 40.0 pg/mL (range 11.6-50.0 pg/mL). All patients were found to have abnormal hypercellular parathyroid glands with a cure rate of 96.7%. When compared to the parathyroid hormone >50 group, the parathyroid hormone ≤50 group was younger (56 ± 15 vs 60 ± 14 years, P < .001) with a lower body mass index (28.7 ± 7.0 kg/m² vs 31.2 ± 7.9 kg/m², P < .001), higher rate of fatigue (73.2% vs 63.0%, P = .033), and higher rate of multiglandular disease (58.9% vs 31.9%, P < .001). There was no difference between the groups with respect to patient demographics, rate of previous parathyroidectomy, surgical cure, or postoperative complications (persistent or recurrent hyperparathyroidism and hypocalcemia).

Patients with hypercalcemia and parathyroid hormone ≤50 pg/mL have a similar clinical presentation and rate of surgical cure to other primary hyperparathyroidism patients and should be considered for parathyroidectomy. Most of these patients have multiglandular disease and thus should be considered for bilateral parathyroid exploration.