Gender differences are also observable at the molecular level, although there is a scarcity of human studies (Lenroot et al. 2007; Schmithorst and Holland 2007). Adolescent brain development is mediated by both sex steroids: androgens (MacLusky et al. 2006) and estrogens (Galea et al. 2006). Sex steroid hormones are involved in brain “organization” that first establish sexual dimorphism of brain morphology leading to sexual behavior and physiology in adulthood, and in brain “activation” to further maintain gender-specific behaviors in adulthood (Cooke et al. 1998). However, the role of sex steroids and hormones on brain development was investigated only by a few neuroimaging studies.
