Major new finding: Will the discovery of a possible gene linked to transssexualism help break down some of the stigma attached to transsexuals? Image shows the official transgender symbol.

Credit: MIT OpenCourseWare

“This research suggests that extra-long copies of the androgen receptor (AR) gene potentially affect testosterone function in the brains of male-to-female transsexuals," said Andrew Sinclair, a geneticist at the Murdoch Children’s Research Institute in Melbourne who was not involved with the study.

Sinclair, who agreed with the authors as to the possible mode of action of the gene variant, said that, "these defective copies of the AR gene could severely reduce normal testosterone levels, resulting in a more female-like brain."

"This [study] supports the notion that transsexualism has a biological basis rather than being due to psychosocial factors in early childhood,” he added.

Limitations of study

Other experts, however, argued that the small study population limited the conclusions that could be drawn from the results.

"The investigators themselves point out that numbers in association studies are important and while the numbers in their study are modest, they are still potentially quite low," said Ron Trent, a geneticist at University of Sydney. "While statistically significant, [the results are] only just so and this is a weakness."

“This is still a small sample and the effects of the difference in androgen receptor are not black and white, so obviously there is much more to be done," agreed Jennifer Graves, head of the Comparative Genomics Research Group at the Australian National University in Canberra.

"However, I am perfectly sure it will turn out that there are important genes involved in sexuality," she said.

Call to replicate findings

Juliet Richters, a professor in sexual health at the University of New South Wales, in Sydney, said that while the study does not identify the gene as a cause of transsexualism it might provide some comfort for those with the condition.

“It may be a matter of relief for transsexuals to have their condition identified as genetic, rather being blamed for making an awkward lifestyle choice,” she commented.

Despite the debate, the findings provide a good clue to go hunting for the many factors likely to be involved in transsexualism, said Harley, who now invites other research teams to attempt to replicate his findings.