This difference in the insulin correlation strength was found despite the comparable plasma insulin levels and was supported by the increasing proportion of INSR in CD4+ cells, measured by the INSR/IGF1R expression ratio, of both RA patients and HC (Figure 1D,E; Spearman rho 0.447 RA and 0.549 HC, respectively). Here, INSR is linked to rheumatoid arthritis.