REN and COVID-19: Finally, Vitamin D deficiency is a risk factor for COVID-19 (Biesalski, 2020) that is also related with low levels of ACE2 because Vitamin D inhibits the expression of Renin, which in turn produces Ang1-10, the substrate from which is cleaved Ang1-8, which downregulates ACE2 (Ajabshir et al., 2014).