59 - Gonadal Hormones and Sexual Differentiation of Human Brain and Behavior

Abstract

Gonadal hormones have powerful influences on sexual differentiation of mammalian brain and behavior. This chapter evaluates the role of gonadal hormones in human neural and behavioral development. Studies of individuals who experienced prenatal hormone abnormality, because of genetic problems or because their mothers were treated with hormones during pregnancy, as well as studies relating normal variability in the early hormonal environment with normal variability in behavior, are reviewed. These studies provide substantial evidence that prenatal androgen exposure influences childhood play behavior, including toy, playmate and activity preferences, as well as sexual orientation (i.e., direction of erotic interest). Evidence also suggests influences of androgen during early development on core gender identity (the sense of self as male or female), aggressive behavior, empathy, and hand preferences. Current research activity focuses on expanding information as to the range of behaviors and psychological conditions, including psychological disorders, that are influenced by the early hormonal environment, and on identifying the mechanisms, including changes in neural structure, that underlie hormone-related behavioral changes. These findings have implications for the fundamental understanding of mechanisms of sexual differentiation of brain and behavior and of human gender development, as well as implications for clinical management of individuals with disorders of sex development.