Namely, although increased testosterone concentrations could increase susceptibility to SARS-CoV-2, and portend worse outcomes by up-regulating the expression of transmembrane protease serine 2 (TMPRSS2), testosterone is also known to attenuate oxidative stress and endothelial dysfunction, thus dampening the aberrant immune response operating in severe COVID-19. This evidence concerns the gene TMPRSS2 and endothelial dysfunction.