Previously we reported that serum FGF23 levels were related to inflammation and disease activity of RA, and matrix metalloprotease-3 (MMP-3), which is a bone destruction marker, and to bone absorption marker (serum type I collagen cross-linked N-telopeptide [NTx]) but not to bone mineral density (BMD)2. This evidence concerns the gene FGF23 and rheumatoid arthritis.