17 November 2022

Flu and hormones

Avian flu in men reduces testosterone levels

Alexander Biryuzov, PCR.news

The first cases of human infection with avian influenza virus (H7N9) were reported in 2013 in China. Since then, H7N9 has caused five waves of the epidemic from 2013 to 2017, and each time men were sick more often (68-71% of the number of cases) than women. The reasons for the gender selectivity of avian influenza remain unknown.

Experiments on mice have previously demonstrated that H1N1 infection reduced testosterone levels in males, but not in females, and males with low levels of the hormone had the most severe infection. That's why researchers from Germany and China decided to evaluate the effect of testosterone on the incidence of H7N9 in humans.

369 people were selected for the study, including participants with PCR-confirmed H7N9 infection, patients with PCR-confirmed H1N1 or H3N2 infection, as well as people who had contacts with the H7N9 virus, but with a negative PCR result. Concentrations of sex hormones in the blood were measured in all groups.

In men infected with H7N9, the overall level of circulating testosterone was reduced compared to H7N9-negative participants. Men aged 18-49 tended to have a higher risk of death during infection if overall testosterone levels were low. Among women infected with H7N9, overall testosterone levels were comparable to H7N9-negative controls. In relation to estradiol, the association with infection in men has not been shown. In women, H7N9 infection was associated with elevated estradiol levels only in the group over 50 years of age. The authors talk about the need for additional research.

Scientists have concluded that infection with the H7N9 virus in men, unlike women, is associated with a decrease in total and free testosterone levels. The results confirm the hypothesis that low levels of total testosterone in men aged 18-49 are associated with death. The effect of cytokine and chemokine concentrations on the course of avian influenza is also shown. Elevated levels of G-CSF, GM-CSF, IL-10, MCP-1, TNF-α and IL-15 were associated with death in men infected with H7N9.

An experiment on male mice confirmed that avian flu causes a significant decrease in circulating testosterone levels. Elevated levels of inflammatory cytokines and chemokines were also observed in the testicles of mice infected with H7N9. The authors of the study suggest that testosterone production can be suppressed either directly through local infection and inflammation of the testicles, or through the action of systemic inflammation on the hypothalamic-pituitary-gonadal axis.

Testosterone levels in men infected with the H7N9 virus may serve as a prognostic marker of the severe course of the disease in the future, but this will require further research.

The article by Bai et al. H7N9 avian influenza virus infection in men is associated with testosterone depletion is published in the journal Nature Communications.

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