FGF19 and sarcopenia: Although some biomarkers, such as albumin (ALB), interleukin 6 (IL-6), growth differentiation factor 11 (GDF11), and recently the emerging fibroblast growth factor 19 (FGF19), have been considered as biomarkers related to sarcopenia, the types and mechanisms of these biomarkers have not been clearly defined and accepted internationally (7, 8).