Cinacalcet to Treat Hypercalcemia in Renal Transplant Recipients

Secondary Hyperparathyroidism in the renal transplant recipient can cause abnormal bone and mineral metabolism, resulting in hypercalcemia that is detrimental to renal function, causing renal dysfunction and calcinosis. These patients often require parathyroidectomy to correct the hypercalcemia. Surgery is not without significant risk to the patient. Risks include vocal cord paralysis, protracted hypocalcemia, cardiac arrhythmias, muscle cramps. In addition, parathyroidectomy has been associated with subsequent renal impairment. Cinacalcet is a calcimimetic agent that is very effective in the treatment of secondary hyperparathyroidism in patients with renal failure as well as in hypercalcemia of parathyroid cancer. There have been reports of short term Cinacalcet use in renal transplant recipients. Serum calcium was improved in these patients. However, little is known about the effect of cinacalcet on bone activity and turnover. It is not known whether Cinacalcet causes low turnover bone activity with adynamic bone disease. It is known that low turnover bone disease in renal patients can by itself cause hypercalcemia as the bone becomes static and unable to respond to everyday calcium loads. Studies have shown that adynamic bone can develop in renal transplant recipients under a variety of conditions. It is not known what effect, if any, cinacalcet has on the bone activity of renal transplant recipients with persistent secondary hyperparathyroidism. The purpose of the study is to determine the effect of Cinacalcet on serum calcium, renal function and bone histology in renal transplant recipients. This is a prospective, open-label study. Protocol procedures will include baseline and 6 month measurements of bone mineral density, bone biochemical parameters, glomerular filtration rate, anterior iliac crest bone biopsy. Subjects will start cinacalcet after the first biopsy. The medication will be titrated to normalize serum calcium. Medication will be supplied by the study. Serum electrolytes will be monitored as indicated.