Can testosterone make you sicker?

It’s a scene straight out of an 80’s sitcom: a man and a woman both come down with the flu, but the woman continues on with her responsibilities armed only with a pocket full of tissues, while the man lounges in his pajamas on the couch, surrounded by tea and medicine. But is “man flu” a myth or reality? While men really do experience more severe infections than women do, women are more likely to experience autoimmune disorders. Both of these patterns suggest that men’s immune responses are weaker than women’s, but the exact reason for this isn’t well understood. New research suggests that testosterone might have something to do with it.

What the research says

The research, led by Professor of Microbiology and Immunology Mark Davis, looked at a large number of biomarkers of immune function after flu vaccination in a sample of 53 women and 34 men aged either 20-30 or 60-89 (since testosterone decreases with age, age was also included in the statistical models). Their research identified some genes involved in immune pathways that are likely to be regulated by testosterone. This means that the activity of these genes (their ability to make proteins that decrease immune response) is increased when levels of testosterone are higher. In addition to finding consistent sex differences in both testosterone level and antibody response, researchers also found that men with higher levels of testosterone showed lower levels of antibody response than men with lower levels of testosterone.

What the media said

This research was widely reported, with headlines that invariably mentioned “man-flu” (e.g., The Telegraph and The Independent). Many media outlets suggested that this finding will have implications for those taking part in the increasing trend of taking testosterone supplements, although the study only looked at natural variations in testosterone among 34 men, so such speculation is just that. In general, the media coverage avoided overstating the implications of the study, although, as always, the full story is considerably more complicated than the media coverage.

Why would testosterone impair immune response?

The last paragraph of the paper speculates on the evolutionary significance of this finding, suggesting that high levels of testosterone help more-frequently-injured males to avoid potentially deadly immune over-reactions.

“Because males of many species are more likely to experience trauma than females, this positive effect of testosterone may also help to balance out the consequences of reduced immunity to infection.”

As an evolutionary psychologist who studies human mate choice, I was very interested in the possible functions of this finding for another reason: such a relationship between testosterone and immune function has been predicted for many years by the immunocompetence handicap hypothesis of female mate preferences for masculine features. This hypothesis suggests that there is a tradeoff between testosterone-mediated traits and immune function. In other words, if high testosterone levels have the unfortunate (but potentially unavoidable) side effect of decreasing immune function, then displaying a masculine jawline and a deep, sexy voice (I’m looking at you, Benedict Cumberbatch) while still remaining alive and relatively healthy is a great advertisement for your overall quality. Think of a golf handicap: a good score is all the more impressive if it was obtained by a player with a more severe handicap.

In conclusion, this research definitely doesn’t suggest that you should demand testosterone-blockers next time you get the flu, but you might be inclined to have a bit more sympathy for the men in your life next time they’re ill.

Furman, D., Hejblum, B. P., Simon, N., Jojic, V., Dekker, C. L., Thiébaut, R., Tibshirani, R. J., & Davis, M. M. (2013). “Systems analysis of sex differences reveals an immunosuppressive role for testosterone in the response to influenza vaccination.” Proceedings of the National Academy of Sciences, 201321060. doi: 10.1073/pnas.1321060111