Assessing the risk of hypercalcemic crisis in patients with primary hyperparathyroidism

Hypercalcemic crisis (HC) is a potentially life-threatening manifestation of primary hyperparathyroidism (PHPT). This study aimed to identify patients with PHPT at greatest risk for developing HC.

This retrospective cohort study included patients with a preoperative calcium of at least 12 mg/dL undergoing initial parathyroidectomy for PHPT from 11/2000 to 03/2016. We compared those with HC, defined as needing hospitalization for hypercalcemia, to those without HC.

The study cohort included 29 patients (15.8%) with HC and 154 patients (84.2%) without HC. Demographics and comorbidities were similar between the groups. Patients with HC were more likely to have a history of kidney stones (31.0% versus 14.3%, P = 0.039), higher preoperative calcium (median 13.8 versus 12.4 mg/dL, P < 0.001), higher parathyroid hormone (PTH) (median 318 versus 160 pg/mL, P = 0.001), and lower vitamin D (median 16 versus 26 ng/mL, P < 0.001) than patients without HC. Cure rates with parathyroidectomy were similar, but nearly double the proportion of patients with HC had multigland disease (24.1 versus 12.3%, P = 0.12). In multivariable analysis, higher preoperative calcium (odds ratio [OR] 1.7, 95% confidence interval [CI] 1.1-2.5), higher PTH (OR 1.0, 95% CI 1.0-1.0), and kidney stones (OR 3.0, 95% CI 1.1-8.2) were independently associated with HC. A Classification and Regression Tree revealed that HC developed in 91% of patients with a calcium ≥13.25 mg/dL and a Charlson Comorbidity Index ≥4.

These data indicate that calcium, PTH, and kidney stones are important in predicting who are at greatest risk of HC. The Classification and Regression Tree can further help stratify risk for developing HC and allow surgeons to expedite parathyroidectomy accordingly.