INCREASED SERUM CALCIUM IS NOT COMMON IN HOSPITALIZED PATIENTS WITH PRIMARY HYPERPARATHYROIDISM. A RETROSPECTIVE, OBSERVATIONAL STUDY.

Objective: Serum calcium levels often decrease during acute illness in patients with an intact calcium-regulating system. However, the dynamics of serum calcium levels in hospitalized patients with primary hyperparathyroidism (PHPT) have not yet been described. Methods: Clinical and laboratory data were retrospectively retrieved from the electronic medical records of patients with PHPT before, during, and after hospitalization for various reasons (excluding parathyroid surgery). Results: There were 99 non-selected patients, with asymptomatic, hypercalcemic PHPT, hospitalized for various reasons; 42% were admitted for apparent infectious or septic conditions and 58% were admitted for non-infectious conditions Total serum calcium increased > 0.5 mg/dL in 7.4% of the patients: 10.9% and 2.5% of the patients with non-infectious and infectious conditions, respectively. In 65.7% of the patients, the mean total serum calcium (TsCa), but not albumin-corrected calcium (corrCa), decreased significantly during hospitalization, down to below the upper limit of the reference range. While pre-hospitalization TsCa and corrCa were similar in patients with infectious and non-infectious conditions, during hospitalization TsCa was lower in patients with infectious conditions (p = 0.02). Both TsCa and albumin returned to pre-hospitalization levels after recovery. Conclusions: TsCa increases in a minority of hospitalized PHPT. In the majority of hospitalized patients with PHPT, total serum calcium, but not corrCa, decreases to within the normal reference range, more so in patients with infectious conditions, obscuring the major characteristic of PHPT. Therefore, it is prudent to follow calcium and corrCa during the hospitalization in patients with PHPT.