MSTN and rheumatoid arthritis: Murillo-Saich et al. compared the serum myostatin levels (measured using an enzyme-linked immunosorbent assay) of 84 women with RA experiencing different degrees of disease activity (a disease activity score in 28 joints (DAS28) of 2.8 (0.9–7.1)) and 127 women without rheumatic disease, finding higher levels of myostatin in the RA group (9 (1.2–140) ng/mL) than in the group without rheumatic disease (3.5 (1–89.9) ng/mL) [61].