Men’s blood has higher levels than women’s of a key enzyme used by the new coronavirus to infect cells, the results of a big European study showed on Monday — a finding which may help explain why men are more vulnerable to infection with COVID-19.

Angiotensin-converting enzyme 2 (ACE2) is found in the heart, kidneys and other organs. In COVID-19, the respiratory disease caused by the novel coronavirus, it is thought to play a role in how the infection progresses into the lungs.

The study, published in the European Heart Journal, also found that widely-prescribed drugs called ACE inhibitors or angiotensin receptor blockers (ARBs) did not lead to higher ACE2 concentrations and should therefore not increase the COVID-19 risk for people taking them.