Sex Differentiation: Organizing Effects of Sex Hormones
Men and women differ, not only in their anatomy but also in their behavior. Research using animal models has convincingly shown that sex differences in the brain and behavior are induced by sex hormones during a specific, hormone-sensitive period during early development. Thus, a male-typical brain is organized under the influence of testosterone, mostly acting during fetal development, whereas a female-typical brain is organized under the influence of estradiol, mostly acting after birth, during a specific prepubertal period. Sex differences in behavior reflect sex differences in the brain, mostly in the hypothalamus and the olfactory system, the latter being important in mate selection. There is also evidence, albeit clinical, for a role of testosterone in the sexual differentiation of the human brain, in particular in inducing male gender role behavior and heterosexual orientation. However, whether estradiol is involved in the development of a female brain in humans still needs to be elucidated.
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