Neuroendocrine mechanisms and the aetiology of male and female homosexuality.

Theories on the classification and aetiology of male homosexuality are reviewed, particularly recent hypotheses on the role of prenatal hormonal influences on brain sexual differentiation and subsequent sexual object choice in the male. Female as well as male brain sexual differentiation may be hormonally determined, and so primary homosexuality in both sexes may be due to abnormalities in foetal exposure to hormones, leading first to physical mis-differentiation and later to homosexual behaviour in genetically and phenotypically normal men and women.