Scientists have found a possible explanation for why men may have a greater risk than women for more severe symptoms and worse outcomes from Covid-19 regardless of age.
The researchers from the Wake Forest Baptist Medical Center in the US pointed to female sex hormone estrogen's role in lowering the level of angiotensin-converting enzyme2 (ACE2) in the heart, which may modulate the severity of Covid-19 in women.
The study, published in the journal Current Hypertension Reports, reviewed preclinical data on sex-specific hormone activity, especially estrogen.
"We know that coronavirus affects the heart and we know that estrogen is protective against cardiovascular disease in women, so the most likely explanation seemed to be hormonal differences between the sexes," said the lead author of the review, Leanne Groban, a professor at Wake Forest School of Medicine.
The researchers said the published literature indicated that ACE2, which is attached to cell membranes in the heart, arteries, kidneys and intestines, is the cellular receptor of the coronavirus responsible for Covid-19 infections, and helps bring the virus into the cells of those organ systems.
The review, they said, also pointed to estrogen's lowering the level of ACE2 in the heart, which may modulate the severity of Covid-19 in women.
Conversely, higher levels of ACE2 in tissues could account for why symptoms are worse in men than women, Groban said.
"We hope that our review regarding the role of estrogenic hormones in ACE2 expression and regulation may explain the gender differences in Covid-19 infection and outcomes, and serve as a guide for current treatment and the development of new therapies," Groban said.