Testosterone and the Brain: From Cognition to Autism

Sex and gender matter in all aspects of life. Humans exhibit sexual dimorphism in anatomy, physiology, but also pathology. Many of the differences are due to sex chromosomes and, thus, genetics, other due to endocrine factors such as sex hormones, some are of social origin. Over the past decades, huge number of scientific studies have revealed striking sex differences of the human brain with remarkable behavioral and cognitive consequences. Prenatal and postnatal testosterone influence brain structures and functions, respectively. Cognitive sex differences include especially certain spatial and language tasks, but they also affect many other aspects of the neurotypical brain. Sex differences of the brain are also relevant for the pathogenesis of neuropsychiatric disorders such as autism spectrum disorders, which are much more prevalent in the male population. Structural dimorphism in the human brain was well-described, but recent controversies now question its importance. On the other hand, solid evidence exists regarding gender differences in several brain functions. This review tries to summarize the current understanding of the complexity of the effects of testosterone on brain with special focus on their role in the known sex differences in healthy individuals and people in the autism spectrum.

The CAG polymorphism in androgen receptor (AR) gene impacts the moral permissibility of harmful behavior in females

The moral permissibility of harm is strikingly varied among individuals. In light of the connection between testosterone levels and utilitarian moral judgment, this study examined to what extent a CAG polymorphism in the androgen receptor gene, a genetic polymorphism with the ability to regulate testosterone function, contributes to individual differences in moral judgment. Four hundred and thirty-nine Chinese Han participants completed permissibility ratings of harm in moral dilemmas and moral transgression scenarios. Results showed a significant association between the CAG polymorphism and moral permissibility of harm in females. Females with more copies of the S allele, which is associated with higher availability of testosterone, were more likely to judge harmful utilitarian acts and unintentionally harmful acts as permissible, while these effects were absent in males. The findings provide the first evidence for a link between the androgen receptor gene and moral judgment and highlight the role of androgens in moral foundations.

On the effects of testosterone on brain behavioral functions

Testosterone influences the brain via organizational and activational effects. Numerous relevant studies on rodents and a few on humans focusing on specific behavioral and cognitive parameters have been published. The results are, unfortunately, controversial and puzzling. Dosing, timing, even the application route seem to considerably affect the outcomes. In addition, the methods used for the assessment of psychometric parameters are a bit less than ideal regarding their validity and reproducibility. Metabolism of testosterone contributes to the complexity of its actions. Reduction to dihydrotestosterone by 5-alpha reductase increases the androgen activity; conversion to estradiol by aromatase converts the androgen to estrogen activity. Recently, the non-genomic effects of testosterone on behavior bypassing the nuclear receptors have attracted the interest of researchers. This review tries to summarize the current understanding of the complexity of the effects of testosterone on brain with special focus on their role in the known sex differences.

Genetic polymorphisms related to testosterone metabolism in intellectually gifted boys

Prepubertal testosterone levels are lower in intellectually gifted boys. The aim of this pilot study was to analyze potential genetic factors related to testosterone metabolism in control and gifted boys. Intellectually gifted (IQ>130; n = 95) and control (n = 67) boys were genotyped. Polymorphisms of interests were chosen in genes including androgen and estrogen receptors, 5-alpha reductase, aromatase and sex hormone binding globulin. Significant differences between control and gifted boys in genotype distributions were found for ESR2 (rs928554) and SHBG (rs1799941). A significantly lower number of CAG repeats in the AR gene were found in gifted boys. Our results support the role of genetic factors related to testosterone metabolism in intellectual giftedness. Increased androgen signaling might explain previous results of lower testosterone levels in intellectually gifted boys and add to the understanding of variability in cognitive abilities.