New research is showing why a larger percentage of men—particularly bald men—are having worse Covid-19 outcomes than women.

Researchers at Brown University point to androgens, the group of hormones which causes hair loss in men. They’ve determined androgens are linked to severe cases of Covid-19 and suggest their discovery could be called the “Gabrin Sign,” named for the first U.S. physician to die of Covid-19 in the United States. Dr. Frank Gabrin was bald.