Influence of androgen receptor repeat polymorphisms on personality traits in men.(Research Paper/Article de recherche)(Report)

Introduction

Testosterone influences the structure and function of the brain, both during development and in the adult organism, and is a key factor for the sexual differentiation of this organ. (1,2) Given this influence, it is reasonable to assume that testosterone may be of importance for interindividual differences in personality traits, not least those displaying sexual dimorphism, such as neuroticism, extraversion and proneness to aggression. Supporting this notion, studies suggest that androgen levels may correlate with such traits. (2-10)

The actions of androgens are mediated mainly by androgen receptors (ARs), which are widely distributed throughout the human brain. The AR gene (AR) is located on chromosome Xg11-12 and composed of 8 exons. (11,12) Exon 1, encoding the amino-terminal domain, contains 2 polymorphic trinucleotide repeats: one CAG repeat encoding a polyglutamine stretch (13) and one GGN repeat encoding a polyglycine stretch. (14)

The polymorphic polyglutamine stretch appears to be of importance in the function of the receptor as a transcription factor, tentatively by influencing the interaction between the receptor and various coactivators (relatively short fragments improving this interaction and hence increasing receptor responsiveness). (15-20) The importance of the polymorphic polyglycine stretch for AR function is less explored. Recent in vitro studies indicate that polyglycine repeat length is associated with receptor responsiveness, but the exact nature of these effects is not fully clarified. (21-25) In line with these data, a large number of studies have reported associations between short CAG or GGN repeats and increased risk of prostate cancer and benign prostate hyperplasia (26-29) and decreased risk of infertility in men. (30-32) Although investigations on the influence of AR repeat polymorphisms on human behaviour have been sparse, associations with personality, (33-37) externalizing behaviour (38) and depression (39) have been suggested.

In the present study, we investigated the extent to which the AR repeat polymorphisms are related to personality traits in 2 independent samples of men assessed with 2 personality questionnaires, the Karolinska Scales of Personality (KSP) (35,40,41) and the Temperament and Character Inventory (TCI). (42)

Methods

Participants