A study by Terpos et al. (2011) reported that female RA patients with high or moderate disease activity had significantly elevated serum levels of Dkk-1, sclerostin, and C-terminal cross-linking telopeptide of collagen type-I (CTX), while the osteoprotegerin/RANKL ratio was decreased compared to age-matched healthy, nonosteopenic women [38]. This evidence concerns the gene DKK1 and rheumatoid arthritis.