This study has two objectives: a) to analyse the interactions between testosterone levels and CAG repeat length polymorphism as a modulator of androgen receptor (AR) sensitivity with regard to impulsiveness traits, and b) to evaluate the contribution of other biological variables as Luteinising Hormone, Follicle Stimulating Hormone, Sex Hormone Binding Globulin (LF, FSH, SHBG) and albumin in the relationship between testosterone levels and AR CAG length polymorphism with impulsiveness.