Hypercalcemia due to resistant hyperparathyroidism in renal transplant patients treated with the calcimimetic agent cinacalcet

Introduction and aims. Calcimimetic agents increase the sensitivity of calcium-sensing receptors of parathyroid glands and suppress both serum calcium levels and parathyroid hormone (PTH). The use of these drugs in patients with a functioning graft suffering from resistant hyperparathyroidism and hypercalcemia is still under investigation. We report seven patients who were treated with the calcimimetic agent cinacalcet. Methods. The four male and three female patients of 38 to 72 years of age received a renal transplant from 4 to 35 months before cinacalcet treatment. Serum creatinine was 1.2 to 1.8 mg/dL (estimated glomerular filtration rate between 40 and 75 mL/min). Immunosuppressive treatment consisted of interleukin-2 antibody induction therapy, calcineurin inhibitors (cyclosporine or tacrolimus), prednisolone, and mycophenolate mofetil. Mild to severe hyperparathyroidism resistant to vitamin D analog treatment (intact parathyroid hormone molecule [iPTH] 174 to 519 pg/mL) was accompanied by severe hypercalcemia (Ca > 11 mg%). To date the patients have completed 3 to 18 months of therapy. Cinacalcet 30 mg/d was initially administered. Results. This treatment resulted in a rapid decrease in total serum calcium (8.6 to 9.2 mg/dL) while PTH showed a milder, progressive decrease. Having controlled calcium levels, la OH vitamin D (0.25 mu g/d per os) was added to the treatment, which resulted in a further decline of iPTH without producing an increase in serum calcium concentrations (median initial iPTH value 401 pg/mL, median value after treatment 176 pg/mL). Therapy was well tolerated without hypocalcemic events. Conclusion. Cinacalcet offered a better holistic treatment approach to such patients.