Biology of sexuality inborn determinants of human sexual response.

Opinions vary on the relative importance of biological and learning processes in the aetiology of sexual expression and deviance. The structure of personality, consistency of fantasy patterns, and the familial nature of homosexuality hint at a biological anlage. Research with the HY-antigen complex and X chromosome, and the elucidation of the interactions of intrauterine testosterone and its products with the foetal brain and neurotransmitters, have given us new models to understand the programming of sexuality. However, gonadotrophin feedback is not relevant as an indicator of brain feminization in primates and man. Finally, the interaction of masculinization and defeminization provides us with a model for understanding homosexual behaviour.