A Biochemical Investigation of the Prevalence of Hypercalcemia and Thiazide-Related Hypercalcemia in Patients.

Objective: Hypercalcemia allied with thiazide diuretics is a widely acknowledged clinical presentation. Hence, the purpose of this investigation was to ascertain the prevalence of hypercalcemia and hypercalcemia linked to thiazides and to evaluate serum phosphorous, 25- hydroxyvitamin D, and parathyroid hormone (PTH).

Methods: This prospective, cross-sectional research study involved all patients, including outpatients, and was conducted over a 12-month period. Between December 2017 and December 2018, an aggregate of 373 patients were enrolled. All patients with hypercalcemia (albumincorrected serum calcium > 10.8 mg/dL) had their medical information put on a proforma, together with the results of any tests (such as parathyroid hormone (PTH), 25-hydroxyvitamin D, and serum phosphorus).

Results: Out of 373 subjects, 7 (2%) were hypercalcemic. The mean corrected calcium levels in the normo-calcemic group were 9.46 ± 0.60 mg/dL (95% CI, 9.4 - 9.5), and that in the hypercalcemic group were 11.68 ± 0.82 mg/dL (95% CI, 10.9 - 12.4). Of the seven cases of hypercalcemia, 2 patients (28.6%) had thiazide-associated hypercalcemia (TAH) along with primary hyperparathyroidism (PHPT). Of the remaining 5 hypercalcemia patients, two more had PHPT, and one (14.3%) had hypervitaminosis D, whereas no cause was mentioned in the remaining 2 patients. Among the 4 PHPT patients, corrected calcium was slightly higher in those with TAH vs those without TAH, though the difference was statistically insignificant (11.32 ± 0.43 vs 11.14 ± 0.39 mg/dL; P > 0.7).

Conclusion: TAH is the second primary cause of asymptomatic hypercalcemia after PHPT. Thus, close coordination between the clinicians, pharmacology, pharmacovigilance, and the biochemistry department may help in identifying these cases.