Endocrine Abstracts

Context: Until now the role of medical therapy in patients with primary hyperparathyroidism (PHP) was mainly based on the use of bisphosphonates. Recently, cinacalcet hydrochloride was reported to be effective in control hypercalcemia in PHP. The aim of this study was to evaluate the efficacy of cinacalcet in PHP patients who were not effectively controlled with alendronate.

Patients and methods: Fourteen PHP patients (mean age 64.1±2.6) were included in the study. All patients had received a treatment with alendronate 70 mg a week for two years. The medical therapy with cinacalcet was started at the dose of 30 mg a day after withdrawal of alendronate. Serum concentrations of PTH and calcium as well as bone mineral density (BMD) at the lumbar spine were evaluated before and after treatment.

Results: Serum calcium levels were 10.7±0.2 mg/dl at baseline, raised to 10.9±0.2 mg/dl after two years of treatment with alendronate and decreased to 9.6±0.2 mg/dl after one year of treatment with cinacalcet. At this time, all patients had serum calcium levels in the range of normality. PTH levels were progressively increased during therapy with alendronate, while they were significantly decreased (P<0.05) but not normalized after one year of treatment with cinacalcet. BMD values were significantly increased after alendronate (P<0.05) while unchanged after cinacalcet. Twenty-one % of patients required to increase the dose of cinacalcet to 60 mg a day during follow-up. Cinacalcet was safe and well tolerated.

Conclusion: In PHP patients unresponsive to a long-term treatment with alendronate, cinacalcet rapidly and effectively normalizes calcium levels and significantly reduce PTH levels. BMD was unchanged after one year of treatment with cinacalcet. It remains to evaluate if a combined therapy with bisphosphonates and cinacalcet may induce a better response on bone mineral density.