Theories about the physical origin of homosexuality: -Homosexuality due to hormonal activity: abnormal sexual behavior comes from an imbalance in the proportion of male and female hormones, present both in the blood of both sexes. But tests conducted in homosexual Direct have not produced a result that confirms the theory, has shown no means deficient hormonal distribution. -Intersex: The sex to which an individual belongs is determined at the time of conception, and depends on the genetic variation that corresponds to the sperm that fertilizes the egg. Physical causes of intersexuality have not yet been well defined, is usually caused by an endocrine disorder that occurs during fetal life. There are degrees of intersex varadsimos in some internal sexual glands (ovaries or testes) and physical appearance are contradictory, in other internal sexual glands are mixtures of testes and ovaries, and other external genitalia can present all intermediate stages between male and female, to even have a penis and uterus at one time. -Hereditary: The third and final physical theory of the origin of homosexuality, of concern to West, is that proposed by heredity. West points out that despite the seriousness of these studies, including comparative twin study indicates genetic aspects of male homosexuality, of FJKallman, the vagueness of the evidence presented does not allow us to establish that homosexuality is a constitutional characteristic of type hereditary.