RETN and rheumatoid arthritis: To explore this, in MSD patients we measured serum levels of markers related to bone turnover, i.e., CTX-I, cartilage oligomeric matrix protein (COMP), OPG, and RANKL, as well as adipokines associated with the pathogenesis of RA and OA, i.e., visfatin, adiponectin, leptin, and resistin.