The effect of type TNF-α inhibitor used on serum levels of bone turnover markers, i.e. PINP (a), CTX-I (b) and osteoclastogenesis markers: sRANKL (c) and OPG (d) in female rheumatoid arthritis patients during 15-month therapy. a* p < 0.01 or a** p < 0.001 compared to the baseline. ADA, adalimumab; CTX-I, C-terminal cross-linking telopeptides of type I collagen; ETA, etanercept; OPG, osteoprotegerin; PINP, N-terminal propeptides of type I procollagen; RA, rheumatoid arthritis; sRANKL, total soluble receptor activator of nuclear factor κB ligand; TNFαI, tumor necrosis factor α inhibitors.