INS and rheumatoid arthritis: On the other hand, the TBS was negatively correlated with insulin concentrations, FG, and RA disease activity (respectively, r = −0.45, p = 0.01, r = −0.40, p = 0.03, r = −0.37, p = 0.04), the last one was further negatively correlated with 25-OHD serum concentrations (r = −0.6, p = 0.0006) and insulin-resistance (r = 0.3, p = 0.04).