Sydney, May 14 (IANS) The largest ever genetic study of transsexuals has established a link between gender identity and a gene involved in modifying the action of sex hormone testosterone.
From an early age people develop an inner sense of being male or female. Transsexuals however, identify with a physical sex opposite to their biological sex.

DNA samples were collected from 112 male to female transsexuals and researchers compared genetic differences with non transsexuals.

They discovered that male to female transsexuals were more likely to have a longer version of a gene which is known to modify the action of testosterone.

“We think that these genetic differences might reduce testosterone action and under-masculinise the brain during foetal development,” said researcher Lauren Hare.

For decades, there has been debate over the causes of transsexuality. Early theories included psychosocial factors such as childhood trauma. More recent studies have indicated that family history and genetic aspects are linked to the development of gender identity.

“There is a social stigma that transsexualism is simply a lifestyle choice, however our findings support a biological basis of how gender identity develops,” said study leader Vincent Harley, who heads the Molecular Genetics at Prince Henry’s Institute.

“As with all genetic association studies, it will be important to replicate these findings in other populations,” said Harley, an associate professor, according to a Prince Henry release.

Researchers are now planning even larger genetic studies and are investigating a wider range of genes that may be related to gender identity.

The results were published in Biological Psychiatry.