[Regulation and determinants of sex behavior]

One has to distinguish masculine sex behavior and estrogens alone or in combination with gestagens evoke feminine sex behavior. The central integrator for the induction of sex behavior is located in diencephalic nuclei. If sex hormones are lacking, the sex drive is fading off, except in women. Sex hormones are also responsible for the determination of those neutral centres controlling male or female sex behavior later in life in most species. Based on animal datas and on retrospective inquiries of homosexuals or mothers of homosexuals, a hypothesis for the etiology of homo-, bi- and hyposexuality has been developed by Dorner. Absence or deficiency of androgens in the critical phase of "brain differentiation" leads to male homo-, bi- or hyposexuality, respectively. If androgens become active in the critical phase of female differentiation, then the result will be female homo-, bi- or hyposexuality, respectively. This hypothesis will be critical evaluated.