Cinacalcet lowers FGF-23 level together with bone metabolism in hemodialyzed patients with secondary hyperparathyroidism.

PURPOSE: Secondary hyperparathyroidism (sHPT) is associated with elevated levels of FGF-23, which in turn are connected to adverse outcomes in ESRD patients. The relationship between FGF-23 and bone metabolism in patients with sHPT treated with cinacalcet has not been studied.

METHODS

Thirty-four stable chronically hemodialyzed patients with sHPT were prospectively followed during the treatment with cinacalcet without any changes in concurrent vitamin D or phosphate binder dose. Blood samples were collected at the start and after 6 months of study. Levels of osteocalcin (OC), cross-linked C-telopeptide of type I collagen (CTX), and FGF-23 were measured.

RESULTS

Eighteen patients finished the study. Levels of calcium, phosphate, and iPTH decreased during 6 months of treatment with cinacalcet. Serum level of FGF-23 decreased significantly (log FGF-23 from 7.58 ± 1.7 to 6.61 ± 1.7 pg/ml) (P < 0.001). Cinacalcet lowered the concentration of CTX from 3.1 ± 0.6 ng/ml to 2.6 ± 0.9 ng/ml (P < 0.05) and OC from 91.8 (41.5-558.6) to 70.3 (11.3-419.7) ng/ml (P < 0.05). The magnitude of change in FGF-23 concentration before and after treatment correlated significantly with suppression of osteoblasts' function assessed by ΔOC (r = 0.5, P < 0.05) but not with changes in bone resorption marker ΔCTX.

CONCLUSIONS

Cinacalcet treatment of sHPT results in reduction of FGF-23 levels, probably due to the suppression of osteoblasts function.