<P> In neonatal life, gonadal steroids influence the development of the neuroendocrine hypothalamus . For instance, they determine the ability of females to exhibit a normal reproductive cycle, and of males and females to display appropriate reproductive behaviors in adult life . </P> <Ul> <Li> If a female rat is injected once with testosterone in the first few days of postnatal life (during the "critical period" of sex - steroid influence), the hypothalamus is irreversibly masculinized; the adult rat will be incapable of generating an LH surge in response to estrogen (a characteristic of females), but will be capable of exhibiting male sexual behaviors (mounting a sexually receptive female). </Li> <Li> By contrast, a male rat castrated just after birth will be feminized, and the adult will show female sexual behavior in response to estrogen (sexual receptivity, lordosis behavior). </Li> </Ul> <Li> If a female rat is injected once with testosterone in the first few days of postnatal life (during the "critical period" of sex - steroid influence), the hypothalamus is irreversibly masculinized; the adult rat will be incapable of generating an LH surge in response to estrogen (a characteristic of females), but will be capable of exhibiting male sexual behaviors (mounting a sexually receptive female). </Li> <Li> By contrast, a male rat castrated just after birth will be feminized, and the adult will show female sexual behavior in response to estrogen (sexual receptivity, lordosis behavior). </Li>

What kind of hormones does the hypothalamus release