Early androgen influences on human neural and behavioural development

Gonadal hormones, particularly androgens, influence sexual differentiation of the body, as well as the brain and behaviour. Antenatal exposure to atypical hormone environments leads to alterations in human behaviours that show sex differences. These include childhood play, sexual orientation, gender identity, and personality characteristics, such as empathy and aggression. Individual variability among healthy children in antenatal hormone exposure show similar relationships to individual variability in postnatal behaviour. As in studies of atypical exposure, higher levels of androgen predict more male-typical, and less female-typical, behaviour. Hormone-induced alterations in brain development are thought to underlie these behavioural outcomes, although there is little information on specific neural differences associated with early hormone differences. Notable, however, is evidence relating early androgen exposure to activation of the medial amygdaloid nucleus in women. Other emerging research areas include the role of neonatal hormones in infant development and interactions between hormone-induced predispositions and postnatal experience in producing behavioural outcomes.