New York, Aug 28 : Researchers have revealed that estrogen may lessen the severity of Covid-19 symptoms in women, adding that this may be the reason why men are at a greater risk than women for more severe outcomes from this virus. Estrogens are hormones that are important for sexual and reproductive development, mainly in women. They are also referred to as female sex hormones. For the study, published in the journal Current Hypertension Reports, the research team conducted a review of published 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 lead author Leanne Groban from the Wake Forest Baptist Health Centre in the US. The researchers said the published literature indicated that the angiotensin-converting enzyme2 (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. It helps bring the virus into the cells of those organ systems. According to the research team, the review 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 the symptoms are worse in men than women, the study said. The reasons for the higher male sex-specific Covid-19-related mortality are likely to be multi-fold, including differences in lifestyle (e.g., higher rates of tobacco smoking and alcohol consumption) and innate immunity. "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. "In summary, the accumulating evidence of a somewhat lower rate of Covid-19 disease severity in women needs to be further investigated," the study authors noted. Earlier, several studies revealed that men are more vulnerable to Covid-19 infection. Recently, a study, published in the European Heart Journal, found that men have higher concentrations of ACE2 in their blood than women, a molecule that enables the novel coronavirus to infect healthy cells in men. /IANS