Comparison of the effects of tocilizumab and tumor necrosis factor α inhibitors on hepcidin-25 and anemia-related factors in rheumatoid arthritis. Treatment effects were assessed at two, four, eight and sixteen weeks after the start of biologic drug therapy. Serum hepcidin-25 was quantified using a liquid chromatography-tandem mass spectrometry-based assay system, and other parameters were measured using standard laboratory techniques. (A) Serum levels of hepcidin-25 (Hepc-25), (B) hemoglobin (Hb), (C) serum iron (Fe) and (D) serum ferritin (Ferritin). TCZ, tocilizumab; TNFi, tumor necrosis factor α inhibitors. Values are the means and SEM. *P < 0.01 vs. baseline by paired t-test. #P < 0.01 by paired t-test comparing changes from baseline between the two groups at 16 weeks. NS, not significant.