GDF15 and vitamin D deficiency: Numerous factors have been identified to be associated with the pathogenesis of sarcopenia, including increased production of inflammatory cytokines (such as interleukin‐6), vitamin D deficiency, insulin resistance, and growth hormone and insulin‐like growth factor‐1 deficiency, low plasma irisin, and elevated plasma growth differentiation factor 15 (GDF‐15).8, 9, 10, 11