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, 1alpha OH vitamin D (0.25 microg/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.