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ST. LOUIS (Tribune News Service) — Researchers in St. Louis have found that male patients hospitalized with COVID-19 had more severe cases of the virus if they also had lower testosterone, according to a study released on Tuesday.

The research, released by the American Medical Association, showed that out of a group of 90 male COVID-19 patients seen at Barnes-Jewish Hospital last spring, lower testosterone was associated with increased severity of illness.

The study did not prove that lower testosterone levels caused more severe cases. And crucially, older men, and men with diabetes or obesity — all factors associated with worse COVID-19 outcomes — are also more likely to have lower testosterone. But still, the researchers say the findings shed light on one of the earliest questions that arose when the new coronavirus began spreading across the world.

"Initially when COVID started, and the reports of the demographics started coming in, everyone said the same thing: 'Look, there are more men than women,'" said Dr. Sandeep Dhindsa, professor of medicine at St. Louis University and one of the study's authors.

Some people pointed to behavioral factors, and to underlying health conditions that are more common among men.

"Our study suggests the opposite," Dhindsa said.

When the male patients presented at the hospital, those with severe COVID-19 had average testosterone levels of 53 nanograms per deciliter, compared to men with less severe illness, who had average levels of 151 nanograms per deciliter.

"It was quite a dramatic difference," Dhindsa said.

A blood testosterone level of 250 nanograms per deciliter or less is considered low in adult men. The study notes that sudden changes in physical health, like elective surgery or admission to intensive care, are also linked with low testosterone.

Patients' ages ranged from 22 to 88, and the average age was 63. The study also included 62 female patients, and found no associations between their hormone levels and severity of illness.

The researchers looked at testosterone, estrogen, and a growth hormone called IGF-1. Severe COVID-19 was defined as need for supplemental oxygen, ventilation, admission to intensive care, or death. Of the 152 total patients in the study, 37 died.

Dr. Abhinav Diwan, a professor of medicine at Washington University and senior author of the study, said the patients' low testosterone levels might be a marker of other important factors in COVID-19 severity. And he believes that more research may be warranted on the role of hormones among patients who experience lingering effects of COVID-19 for weeks or months after the initial infection, a condition known as "long COVID."

According to the U.S. Centers for Disease Control and Prevention, men account for 48% of the nation's COVID-19 cases, but 54% of the virus fatalities. In Missouri, men account for 46% of Missouri's known COVID-19 cases, but 53% of the known, virus-related deaths, according to data from the state Department of Health and Senior Services.

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