Objectives. The aim of the study was to assess the effect of chronic lithium treatment on serum calcium concentration and the parathyroid function when hypercalcemia was detected in bipolar patients, and to compare the results with age and sex matched patients who had never been exposed to lithium.
Material and methods. The study comprised 90 patients aged 60±10 years who received lithium for mean 16±10 years and 30 patients, aged 56±12 years, never exposed to lithium. The serum calcium levels were measured in all patients. In lithium-treated subjects, the parameters of kidney function and novel biomarkers of kidney injury were assessed. Serum parathyroid hormone levels were assessed in lithium- treated patients with hypercalcemia. Abdominal USG examinations were also carried out.
Results. Patients who received lithium had significantly higher mean serum calcium concentrations, compared with the control group. Hypercalcemia was found in 10% of long-term lithium-treated patients, more frequently than in the control group. The prevalence of hypercalcemia was higher among lithium-treated women than in men. In lithium-treated patients no association between serum calcium levels and age or duration of lithium treatment were found. Hyperparathyroidism was found in 3 out of 9 lithium-treated patients with hypercalcemia. The incidence of nephrolithiasis was more frequent in lithium-treated patients.
Conclusions. The results of the study confirm that long-term lithium treatment is associated with irregularities in calcium metabolism and parathyroid function and suggest, similarly to the results obtained by other researchers, that monitoring of serum calcium concentrations in lithium- treated patients is necessary.