Oral Versus Intravenous Iron Supplementation for the Treatment of Iron Deficiency Anemia in Patients on Maintenance Hemodialysis—Effect on Fibroblast Growth Factor-23 Metabolism

Abstract

Iron administration affects serum levels of intact (I-) fibroblast growth factor-23 (FGF23) and its cleavage product C-terminal (C-) FGF23 in iron-deficient patients on maintenance hemodialysis (MHD). The objective of this study was to compare the effect of oral or intravenous iron administration on serum levels of I-FGF23 and C-FGF23 in iron-deficient patients on MHD. A prospective randomized study. Participants on MHD with severe iron deficiency (n=61). Participants were randomized to receive oral iron (50mg of sodium ferrous citrate daily; oral group, n=29) or intravenous iron (40mg of saccharated ferric oxide weekly; IV group, n=32). Changes in I-FGF23 and C-FGF23 after 10 weeks of treatment. Iron supplementation significantly increased hemoglobin, mean corpuscular volume, ferritin, and transferrin saturation rate, and decreased erythropoiesis-stimulating agent dose and erythropoiesis-stimulating agent resistance index value. Serum phosphate, calcium, and intact parathyroid hormone levels did not change significantly during the study. I-FGF23 levels increased significantly in the IV group and did not change in the oral group, whereas C-FGF23 levels were significantly reduced in both groups. Serum interleukin-6 and tumor necrosis factor-α levels were increased in both groups. Multiple regression analysis indicated the relationship between iron or erythropoiesis and FGF23 metabolism. Iron administration to patients on MHD with severe iron deficiency decreased C-FGF23 levels, whereas intravenous iron increased I-FGF23 levels though oral iron did not. If the target of chronic kidney disease-mineral and bone disorder therapy is reducing I-FGF23 levels, we suggest the use of oral iron.