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If you ever wondered why men seem to get a bit crankier than women when they get the flu it turns out that it's because men are likely to suffer more, according to scientists at Stanford University School of Medicine. And you'll be surprised to know why.
Testosterone, the hormone that makes men manly, according to a study published two weeks ago in the Proceedings of the National Academy of Sciences, appears to weaken the response of men's immune system to an influenza vaccine, according to a report from Stanford.
The study highlighted that men with higher levels of testosterone circulating in their body benefited less than women and men with lower testosterone levels from protective antibodies after a vaccination against influenza.
"This is the first study to show an explicit correlation between testosterone levels, gene expression and immune responsiveness in humans," said the study's senior author, Mark Davis, professor of microbiology and immunology and director of Stanford's Institute for Immunity, Transplantation and Infection. "It could be food for thought to all the testosterone-supplement takers out there."
"Most studies don't report on sex differences, a major determinant of variation in immune response," added the study's lead author, David Furman.
The study analyzed samples from 53 women and 34 men showing that, on average, women had significantly stronger antibody responses to the influenza vaccine which was consistent with other studies.
"This was not surprising," explained Furman.
Women in the study also showed higher average pre-vaccination blood levels of pro-inflammatory immune-signaling proteins, as earlier studies have also found. Pre-vaccination levels of those proteins in a particular woman's blood, however, did not significantly predict the degree of her post-vaccination antibody response.
The analysis of the study also showed that in men, "elevated activity of a particular set of genes that tend to turn on and off at the same time was associated with a weakened antibody response to the vaccine," according to the Stanford report.