Experience with cinacalcet in primary hyperparathyroidism: results after 1 year of treatment.

OBJECTIVES: To assess the characteristics of patients with primary hyperparathyroidism (PHPT) treated with cinacalcet and to evaluate its efficacy in reducing serum calcium and parathyroid hormone (PTH) concentrations after 1 year of treatment.

METHODS: The study included 20 patients with PHPT who had completed at least 12 months of treatment with cinacalcet (eight patients for refusal of parathyroidectomy, three for surgery not possible due to comorbidities and nine for progressive hypercalcemia prior to surgery). We recorded clinical and biochemical data at baseline, and after 3, 6 and 12 months of treatment. We also monitored adverse events. Cinacalcet was administered in increasing doses until normal serum calcium was reached or side effects preventing a further increase occurred.

RESULTS: After 3 months of treatment, serum calcium significantly decreased (11.73 ± 0.85 versus 10.71 ± 1.63 mg/dl, p < 0.001) and serum phosphorus significantly increased (2.41 ± 0.48 versus 2.63 ± 0.70 mg/dl, p = 0.004) while no significant change occurred in PTH (181.91 ± 102.37 versus 195.47 ± 111.71 pg/ml, p = 0.695). No further variation was observed after 6 months compared with 3 months of follow up. However, after 12 months of treatment, there was a significant decrease in PTH concentrations compared with baseline (181.91 ± 102.37 versus 152.47± 70.16 pg/ml, p = 0.028) as well as serum calcium (11.73 ± 0.85 versus 10.20± 0.95 mg/dl, p < 0.001); serum phosphorus significantly increased (2.41 ± 0.48 versus 2.71 ± 0.43 mg/dl, p = 0.01). Normocalcemia (S-Ca < 10.2 mg/dl) was achieved in 55% of patients. The medication was usually well tolerated (83.4%). Most common adverse events were nausea and vomiting, especially at the beginning of therapy.

CONCLUSION: Cinacalcet rapidly reduced serum calcium in patients with PHPT and this reduction remained stable after 1 year of treatment. We also observed a decrease in PTH. Cinacalcet is an effective alternative in nonsurgical treatment of PHPT and may be useful in the preoperative hypercalcemia management.