Men that are hospitalized with Covid-19 appear to experience a significant drop in testosterone levels after falling sick. This could be an important piece of the puzzle in explaining why men tend to fare worse against severe Covid-19 infection compared to women. It's not the first time decreased testosterone levels have been linked to Covid-19, but it is the first time researchers claim it's been shown Covid-19 may cause depletion.
Reporting in the peer-reviewed journal The Aging Male, researchers in Turkey found that male patients' testosterone levels “significantly decreased” while they were sick compared to pre-Covid levels, and the severity of the testosterone decrease was tightly linked to an increased chance of ending up in an intensive care unit (ICU).
“In our study, the mean total testosterone decreased, as the severity of the COVID-19 increased," explained lead author Selahittin Çayan, Professor of Urology at the University of Mersin School of Medicine, in a statement. "The mean total testosterone level was significantly lower in the ICU group than in the asymptomatic group. In addition, the mean total testosterone level was significantly lower in the ICU group than in the Intermediate Care Unit group."
The link between Covid-19 and testosterone has been raised before, and though this research doesn't definitively prove Covid causes the decrease, the data strongly suggests the infection may deteriorate men's testosterone levels similarly to how other infections do. Evidence has previously shown that testosterone dampens the body’s immune response to infections, while estrogen can improve the immune system and increase immune inflammation. It also is known that testosterone levels can decrease during other infections, most likely as a way for the body to redirect energy away from the high-energy tasks associated with the hormone, such as boosting muscle, aggression, and sexual appetite. This has led some scientists to speculate this decrease may be the reason why men are twice as likely to die from Covid-19 as women.
"Testosterone levels have long been known to drop the following onset of disease, and in particular, during infections. There are evolutionary reasons for that which are not necessarily bad," Dr Daniel Kelly, a Senior Lecturer of biochemistry at Sheffield Hallam University, who was not involved in the study, told IFLScience.
"Testosterone is known to be anti-inflammatory, so there is a possibility that exaggerated reduced testosterone may allow the 'cytokine storm' to take hold."
The new study does have some limitations, namely that it did not include a control group of patients with conditions other than Covid-19, meaning it’s not possible to definitively say the infection was the direct cause of the drop in testosterone. The study was also relatively small as it only included patients who had their testosterone levels analyzed before and during their illness. Dr Kelly also explains that other underlying health conditions could also explain this observation.
"In terms of the study delineating a causal relationship between low testosterone and Covid-19 prognosis, it is hard to do," Dr Kelly said. "Did these patients also have an underlying chronic disease that would both lower their baseline testosterone and increase the severity of Covid-19? For example, diabetes is a risk factor for Covid-19 severity and diabetic males have lower circulating testosterone."
Nevertheless, in light of their findings, the researchers say that doctors should consider monitoring testosterone levels shortly after diagnosing Covid-19 and use this information to manage their treatment.
“It could be recommended that at the time of COVID-19 diagnosis, testosterone levels are also tested,” said Professor Çayan. "In men with low levels of sex hormones who test positive for COVID-19, testosterone treatment could improve their prognosis. More research is needed on this.”