TNF and chronic obstructive pulmonary disease: Other markers have also been identified, such as copeptin (a marker of endogenous stress) and pro-inflammatory cytokines like IL-6 and tumor necrosis factor (TNF-α), which increase after intense physical exertion and may play a role in the pathogenesis of myocarditis, cardiac arrhythmias, and fibrosis [41,42,43,44,45].