Last week, doctors on Long Island in New York started treating Covid-19 patients with estrogen in an effort to increase their immune systems, and next week, physicians in Los Angeles will start treating male patients with another hormone that is predominantly found in women, progesterone, which has anti-inflammatory properties and can potentially prevent harmful overreactions of the immune system.

“There’s a striking difference between the number of men and women in the intensive care unit, and men are clearly doing worse,” said Dr. Sara Ghandehari, a pulmonologist and intensive care physician at Cedars-Sinai in Los Angeles who is the principal investigator for the progesterone study. She said 75 percent of the hospital’s intensive care patients and those on ventilators are men.

And pregnant women, who are usually immunocompromised but have high levels of estrogen and progesterone, tend to have mild courses of the disease. “So something about being a woman is protective, and something about pregnancy is protective, and that makes us think about hormones,” Dr. Ghandehari said.