Endocrine Abstracts

Introduction: Parathyroid hormone (PTH) secretion is regulated by the concentration of extracellular ionized calcium. The calcium sensing receptors (CaSR) of parathyroid chief cells play a central role in calcium homeostasis. Their activity is reduced by calcimimetics, the compounds that directly increase the sensitivity of CaSR to extracellular ionized calcium. Cinacalcet hydrochloride, an oral calcimimetic, is indicated in treatment of primary hyperparathyroidism (PHP), for patients with failure of previous surgery, patients with serious comorbidity that makes surgery impossible, or patients who do not accept surgery or do not carry out the surgical criteria.

Aim: To assess the efficacy, tolerability and safety of cinacalcet in the patients with PHP.

Patients and methods: Project is an ongoing prospective two center study in 33 patients (29 women) with PHPT, mean age 64.0 years (95% CI 55.4–74.6). Frome these, surgery was contraindicated in 16 patients, in 12 patients previous surgery failed, and 5 patients did not accept surgery. Serum concentrations of calcium, iPTH, phosphates were evaluated before and during the treatment.

Results and conclusion: All patients responded to cinacalcet. Applied doses of cinacalcet ranges from 15 to 90 mg. Serum calcium was 2.80 mmol/l (95% CI 2.74–2.86) at baseline, iPTH concentration was 19.5 pmol/l (95% CI 15.6–28.4) and phosphatemia was 0.83 mmol/l (95% CI 0.76–0.89). After 6 months, mean calcium concentration was 2.35 mmol/l (95% CI 2.27–2.44) (P<0.001) and mean iPTH concentration was 14.5 (95% CI 11.4–17.7) (P<0.001). The most common adverse event was nausea, which affected 5 patients. Cinacalcet effectively normalizes calcium concentration and significantly reduces (but not normalizes) iPTH concentration. Therapy is safe and well-tolerated.