Therefore, we hypothesized that the observed hypomethylation of CXCL12_22 and FGF21_59 in moderate sarcopenia might indicate a compensatory increased secretion of CXCL12 and FGF21, whereas sustained secretion may result in decreased levels of these two factors, reflecting as hypermethylation of CXCL12_22 and FGF21_59 in patients with severe sarcopenia. The gene discussed is FGF21; the disease is sarcopenia.