Lower testosterone, worse disease—but why remains unclear
Throughout the pandemic, men have consistently faced graver outcomes from COVID-19 than women, and science has long searched for the biological thread that explains this disparity. A new study from Washington University, published in JAMA Network Open, offers a surprising turn: among hospitalized men, it was not an abundance of testosterone but its absence that correlated with severity, ventilator use, intensive care, and death. The finding dismantles an early and intuitive hypothesis, replacing certainty with a more humbling question — whether low testosterone is a cause of vulnerability or merely a signal that something deeper is already failing.
- Men have died from COVID-19 at higher rates than women throughout the pandemic, creating urgent pressure on researchers to understand why.
- The dominant early theory — that high testosterone was amplifying the virus's damage in men — has been contradicted by data drawn from 90 hospitalized male patients.
- Lower testosterone levels tracked with every measure of disease severity: ventilator need, ICU admission, and mortality, with 25 of 37 total deaths occurring in men with the lowest hormone levels.
- Women in the same study showed no hormonal correlation with disease severity, suggesting the testosterone dynamic is specific to male biology.
- Researchers caution that correlation is not causation — low testosterone may be a symptom of some other failing process rather than the driver of worse outcomes.
- The mechanism connecting low testosterone to severe COVID-19 remains entirely unknown, leaving the most important question open for the next wave of investigation.
When men arrived at Barnes-Jewish Hospital with COVID-19, they were consistently sicker than their female counterparts — a pattern doctors had observed across the entire pandemic. One widely circulated theory held that testosterone itself was to blame: men have more of it, the thinking went, and perhaps that excess was amplifying the virus's destruction. A new study published in JAMA Network Open dismantled that assumption.
Researchers at Washington University School of Medicine drew blood from 152 hospitalized COVID-19 patients — 90 men and 62 women — measuring hormone levels and tracking disease progression. What they found inverted the prevailing hypothesis. Among men, lower testosterone correlated with worse outcomes across every meaningful measure: ventilator dependence, ICU admission, and death. Of the 37 patients who died during the study period, 25 were men, and those men tended to have had the lowest testosterone levels of all.
Women showed no such pattern. Hormone levels did not predict severity in female patients, suggesting the testosterone dynamic was particular to male physiology.
The researchers were deliberate in limiting their claims. Correlation is not causation, and the study could not determine whether low testosterone was actively worsening COVID-19 outcomes or simply serving as a visible marker for some other underlying biological failure. Both possibilities remain open. What the study closes, however, is the earlier assumption — that testosterone abundance was the danger. The question of why its absence appears so consequential now waits for the next round of science to answer.
When men arrived at Barnes-Jewish Hospital with Covid-19, they tended to be sicker than the women who came through the same doors. Doctors had noticed this pattern across the pandemic—a stubborn, consistent gap in how the virus treated men versus women. The question was why. One prevailing theory pointed to testosterone itself. Men have more of it than women do, the thinking went, so perhaps that abundance was working against them, amplifying the virus's damage. A new study published in JAMA Network Open upended that assumption.
Researchers at Washington University School of Medicine in St. Louis drew blood from 152 hospitalized Covid-19 patients: 90 men and 62 women. They measured hormone levels in those samples and tracked how sick each patient became. What they found was counterintuitive. Among the men, testosterone levels did correlate with disease severity—but in the opposite direction from what many had suspected. The lower a man's testosterone, the worse his Covid-19 infection tended to be.
The pattern held across multiple measures of severity. Men with the lowest testosterone levels faced the highest risk of requiring a ventilator. They were more likely to need intensive care. They were more likely to die. Among the 143 patients admitted to the hospital during the study period, 37 died overall. Twenty-five of those deaths were men, and the men who died tended to have had lower testosterone levels than those who survived.
Women in the study showed no such correlation. Hormone levels—testosterone or otherwise—did not predict how severely Covid-19 would affect them. The finding suggested that whatever was happening with testosterone and male Covid-19 outcomes was specific to men.
But the researchers were careful about what they claimed to have found. A correlation is not a cause. Low testosterone might indeed be driving worse outcomes. Or it might be a marker, a visible sign that something else entirely was going wrong in the body—some other biological process that both lowered testosterone and made the virus more dangerous. The study could not distinguish between these possibilities. It could only show that the two things moved together: lower testosterone, worse disease.
The result challenges an intuitive but apparently incorrect assumption that had circulated among some researchers early in the pandemic. If testosterone were the culprit, you would expect men with high levels to suffer most. Instead, the opposite appears true. What remains unclear is the mechanism. Why would low testosterone leave men more vulnerable to severe Covid-19? What biological pathway connects the two? Those questions remain open, waiting for the next round of investigation.
Citas Notables
The study could not prove that low testosterone is a cause of severe Covid-19; low levels could simply serve as a marker of some other causal factors.— Washington University School of Medicine in St. Louis
La Conversación del Hearth Otra perspectiva de la historia
So the initial theory was that testosterone itself was making men sicker?
Yes. Men were clearly doing worse with Covid-19 overall, and since men have more testosterone than women, it seemed logical that the hormone might be part of the problem.
But this study found the opposite.
It did. Among the men they studied, those with lower testosterone had more severe disease. The lowest levels corresponded with ventilator use, ICU admission, and death.
Does that mean low testosterone causes severe Covid-19?
Not necessarily. It could be a marker of something else—another underlying condition or biological state that both lowers testosterone and makes the virus more dangerous. The study showed correlation, not causation.
What about the women in the study?
Interestingly, hormone levels didn't predict disease severity in women at all. Whatever is happening with testosterone and Covid-19 appears to be specific to men.
So what's next?
Researchers need to figure out the mechanism. Why does low testosterone correlate with worse outcomes? That's the real question.