Various researches have given biological explanation of transsexualism. The recent Australian study showed that genetics play a crucial role in determining people's sense of gender. The study focused on the potential differences in three genes known to be involved in sex development - coding for the androgen receptor, the oestrogen receptor and an enzyme which converts testosterone to oestrogen.

Researches compared DNA samples of 112 male-to-female transsexuals with 250 typical men. The comparison showed that transsexuals were more likely than non-transsexuals to have a longer version of the androgen receptor gene.

Earlier research has shown that longer versions of the androgen receptor gene are associated with less efficient testosterone signalling.
Lauren Hare of Prince Henry's Institute said: "We think these genetic differences might reduce testosterone action and under-masculinise the brain during foetal development."

Vincent Harley, head of molecular genetics at Prince Henry's Institute said that there is a social stigma that transsexualism is simply a lifestyle choice. However, our findings support a biological basis of how gender identity develops.