• Graves’ disease;
  • hyperthyroidism;
  • ionized calcium;
  • parathormone;
  • parathormone-related peptide

Eur J Clin Invest 2010; 41 (1): 93–97


Background  Hypercalcemia occurs in 10–20% of patients with hyperthyroidism, but its pathogenesis is still unclear.

Aim  To evaluate changes in parathyroid hormone-related peptide (PTH-rP) concentration in hyperthyroid patients compared with healthy controls.

Methods  We studied PTH-rP, parathormone (PTH) and ionized calcium levels in 153 hyperthyroid patients, and 89 control subjects. These variables were revaluated after attainment of euthyroidism with the antithyroid drug carbimazole for 6 months in a subgroup of 47 patients.

Results  Pretreatment PTH-rP and ionized calcium level were significantly higher in hyperthyroid patients than in controls, whereas an opposite trend occurred for PTH. All parameters normalized after carbimazole therapy.

Conclusion  Untreated hyperthyroid patients exhibited a significant elevation in serum ionized calcium and PTH-rP and a significant reduction in serum PTH levels when compared with healthy controls. Our data favoured the hypothesis of a direct involvement of PTH-rP in the pathogenesis of hypercalcemia in hyperthyroid patients.