Effect Of Phosphate Binders On Serum FGF-23Levels In Maintenance Hemodialysis Patients With Hyperphosphatemia

Objective:Recent studies show that elevation of FGF-23is independently associated with progression of renal disease, cardiovascular mortality and left ventricular hypertrophy. Dietary restriction of phosphate and phosphate binders are used for control of phosphate balance and elevation of serum FGF-23levels. The aim of this study is to compare the effect of lanthanum carbonate vs. calcium carbonate on serum FGF23levels in maintenance hemodialysis patients with hyperphosphatemia.Methods:56patients from our Nephrology outpatient clinic with maintenance hemodialysis were included. Patients were on hemodialysis for at least3months prior to enrollment. The mean hemodialysis duration was4h, and all patients had received hemodialysis three times a week. The mean dialysate calcium concentration was2.5mEq/L. The conditions of hemodialysis were fixed throughout the study period. Patients enrolled had serum phosphorus>1.77mmol/L, serum calcium<2.38mmol/L,25-OH-VitD levels>30ng/mL, and serum albumin>30g/L. Patients received dietary restriction of phosphate less than1000mg/day. Then patients were randomized in a1:1ratio to receive either lanthanum carbonate or calcium carbonate during a16weeks period. Blood samples were obtained for routine evaluation of serum calcium and phosphate at2-week intervals; the dose of phosphate binders was adjusted to maintain serum phosphate to reach the target. Serum FGF-23and iPTH levels were measured at Weeks0,4and16.Results:Fifty patients completed the16-week study; four patients discontinued the study due to gastrointestinal symptoms in lanthanum carbonate group, and two patients withdrew the study due to taking medicine irregularly in calcium carbonate group. In both groups, the serum phosphorus level was significantly decreased throughout the treatment period compared with before treatment (P<0.05). Serum corrected calcium level showed little change in both groups. The product of serum corrected calcium and phosphorus (Ca x P product) showed a significant decrease after16weeks of treatment in both groups (P<0.05). The iPTH level showed little change in both groups. In both groups, serum FGF-23levels were similar at baseline. It showed a significant decrease after lanthanum carbonate therapy. On the other hand, the FGF-23level showed little change in calcium carbonate group. Furthermore, a significant correlation was demonstrated between the changes of serum FGF-23and that of serum phosphate. As the reduction of serum phosphate became more marked, the decrease of serum FGF-23also became greater.Conclusions:In maintenance hemodialysis patients, lanthanum carbonate is effective in reducing serum phosphorus levels and FGF-23levels. However, calcium carbonate does not reduce FGF23levels. Thus, lanthanum carbonate may also contribute to improving the survival of CKD patients through reduction of circulating FGF-23as well as providing effective treatment of hyperphosphatemia.