A gene linked to male-to-female transsexualism has been uncovered by Australian researchers. Following a similar finding for female-to-male transsexuals announced in July, the work strengthens the idea that transsexualism has a biological basis.

The study of 112 male-to-female volunteers – the biggest of its kind to date – found that they were more likely than normal males to have a long version of a gene that helps testosterone bind to cells, which could reduce its effects in the body.

The biological bases for gender identity are largely unknown, “but we could speculate that [effective] testosterone signalling is required for male gender identity”, says Vincent Harley at Prince Henry’s Institute for Medical Research at Monash University in Melbourne, Australia, who led the work. “This signalling is weakened in male-to-female transsexuals, leading to decreased masculinisation of their brains”.

Andrew Sinclair, director of early development and disease at the Murdoch Childrens Research Institute in Melbourne agrees.


The work “supports the notion that transsexualism has a biological basis rather than being due to psychosocial factors in early childhood,” he says. “However the finding does not explain all male-to-female transsexuals, suggesting that multiple genetic factors are involved.”

While the genetic link was statistically significant, it was weak – 55% of the transsexuals had the long version of the gene, compared with 50% of normal men. Harley agrees that many more genes related to male-to-female transsexualism probably remain to be discovered.

A better understanding of this would also help in assigning sex to children born with ambiguous genitalia, which is a much more common condition than transsexualism, Harley says.

Journal reference: Biological Psychiatry (in press)

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