Researchers have found that men seem to bemore vulnerable to COVID-19 than women. It suggested the reason might be related to the concentration of the enzyme Angiotensin-Converting Enzyme 2 (ACE2) in the blood of men and women. Key Findings: TheACE2 enzyme in blood responds to the novel coronavirus and enables it to infect the human cell. ACE2 is also a receptor present on the surface of healthy cells. TheSARS-CoV-2 virus uses this receptor to enter inside cells. ACE2 receptors are present in abundance in the lungs, heart, kidneys, and testes. The study found men have higher concentrations of ACE2 in their blood than women. It also showed heart failure patients who are taking a certain class of drugs, called RAAS inhibitors, did not have higher concentrations of ACE2 in their blood. But, some studies suggested RAAS inhibitors might increase ACE2 concentrations in blood plasma.