The molecular mechanisms which may facilitate this male predisposition for severe COVID-19 are currently investigated, with particular focus placed on the role of angiotensin-converting enzyme 2 (ACE-2) which is activated by the SARS-CoV-2 spike proteins and acts as one of the key mediators for SARS-CoV-2 entry into host cells [8, 28–30]. Here, ACE2 is linked to COVID-19.