TMPRSS2 and obesity due to melanocortin 4 receptor deficiency: Furthermore, during SARS-CoV-2 infection, TMPRSS2 expression significantly decreases [9], while pre-existing conditions, like diabetes, obesity, Barrett’s esophagus or autoimmune disease, show higher TMPRSS2 expression and are associated with a more severe course of SARS-CoV-2 [11].