It has long been noted that men are typically more susceptible than females to infections caused by parasites, fungi, bacteria and viruses, and a new study by scientists at Stanford University have made progress in advancing our knowledge behind this puzzling gender difference.

Researchers at Stanford University have managed to link poor immune system response to high testosterone levels in men via immunological response to the influenza vaccine. The study showed that women tended to have a more robust antibody response to the vaccination than did the average man. However, when men with lower than average testosterone levels were tested, they exhibited nearly equivalent responses to that of the females suggesting that higher levels of testosterone were to blame for the weaker immune system response.

Though testosterone does not seem to directly halt the immune response, it does seem to interact with a certain set of genes that seem to blunt the response. According to Mark Davis, PhD, professor of microbiology and immunology at Stanford, “This is the first study to show an explicit correlation between testosterone levels, gene expression and immune responsiveness in humans…It could be food for thought to all the testosterone-supplement takers out there.”