No Evidence for the Immunocompetence Handicap Hypothesis in Male Humans

This study, involving 97 healthy men, investigated the relationship between testosterone levels and immune function, challenging the immunocompetence handicap hypothesis (ICHH), which suggested that high testosterone levels suppress immunity. The research found that free testosterone and, to a lesser extent, DHT were positively correlated with a stronger immune response to influenza vaccination, while total testosterone and DHEA showed no significant immunomodulatory effects. These findings did not support the ICHH, indicating that in affluent societies, men with higher free testosterone levels could invest more in adaptive immunity. The study concluded that androgens should be considered as immunomodulators rather than inherently immunosuppressive.