ADAM-17 levels in RA serum (n = 23) were significantly higher than those in OA serum (n = 16) and NL serum (n = 7) (2093 ± 539 pg/ml, 121 ± 53 pg/ml and 0 ± 0 pg/ml, p < 0.05, respectively, Fig. 1a). Here, ADAM17 is linked to rheumatoid arthritis.