Sex-dependent toxoplasmosis-associated differences in testosterone concentration in humans.

Several lines of indirect evidence suggest that subjects with latent infection of the coccidian parasite Toxoplasma gondii have a higher concentration of testosterone than uninfected controls. Here, we searched for direct evidence of latent toxoplasmosis-associated differences in testosterone concentration among a population of 174 female and 91 male students screened for Toxoplasma infection. We have found Toxoplasma-infected men to have a higher concentration of testosterone and Toxoplasma-infected women to have a lower concentration of testosterone than Toxoplasma-free controls. The opposite direction of the testosterone shift in men compared to women can explain the observed gender specificity of behavioural shifts in Toxoplasma-infected subjects.