Estrogen and ACE2 expression might be factors[1]: > Intriguingly, infection with SARS-CoV induces ACE2 down-regulation through binding of the viral Spike prote

Estrogen and ACE2 expression might be factors[1]: > Intriguingly, infection with SARS-CoV induces ACE2 down-regulation through binding of the viral Spike protein to ACE2, thus reducing ACE2 expression in the lung and igniting acute respiratory failure. Since COVID-19 and SARS patients share similar acute respiratory distress syndrome and a similar gender bias in disease susceptibility and case fatality rates, it is reasonable to believe that they share similar pathogenic mechanisms. > Estrogen, the primary female sex hormone, has been observed to play a protective role in SARS not only by activating immune response but also suppressing directly SARS-CoV replication. To note, estrogen inhibits the activity or expression of different components of the renin–angiotensin system. In particular, estrogen is able to upregulate the expression of ACE2. [1] https://www.nature.com/articles/s41420-020-0276-1 https://www.nature.com/articles/s41420-020-0276-1