Myhre et al. [15] also found a positive correlation between serum GDF-15 levels and the presence of fatigue in COVID-19 patients, which strongly supports the role of GDF-15 as a biomarker of muscular and myocardial affection in COVID-19 patients and could suggest the potential role of GDF-15 as a therapeutic target for Long COVID fatigue. The gene discussed is GDF15; the disease is COVID-19.