From the AAP October 26, 2008:
The nature versus nurture debate rages on but a new study of
transsexuals has shown genetics plays a key role in determining our
sense of gender.
In the largest genetic study of its kind, 112 male-to-female
transsexuals took part in a study involving several Melbourne research
bodies and the University of California, Los Angeles.
Researchers measured the variation in the androgen receptor gene, which
is involved in the functioning of the sex hormone
testosterone.
DNA samples from the transsexuals were compared with the samples from
250 typical men.
Researchers discovered the transsexuals were more likely than
non-transsexuals to have a longer form of the gene.
"We think these genetic differences might reduce testosterone action and
under-masculinise the brain during foetal development,"
Prince Henry's Institute researcher Lauren Hare said.
Lead researcher, Associate Professor Vincent Harley, head of molecular
genetics at Prince Henry's Institute, said there had long been
debate about the causes of transsexuality.
"There is a social stigma that transsexualism is simply a lifestyle
choice. However, our findings support a biological basis of how
gender identity develops," he said.
He said researchers were recruiting transsexual people for another study
and hoped to double the sample size and examine other genes.
Assoc Prof Harley said it was important to replicate the findings in
other populations.
Researcher Trudy Kennedy, director of the Monash Gender Dysphoria
Clinic, said the study supported other evidence that genetics and
brain gender were important in transsexuality.
"This is something that people are born with and it's certainly not a
lifestyle choice as some have suggested," she said.
Julie Peters, a transgender person, said she knew from as young as three
or four years old she did not fit into being a boy.
"I have always had the personality of a girl, I suppose is the way I
perceive it and even from a very young age, three or four, I was
really mad at people for making me a boy," she told AAP.
"I personally think it (gender) is a combination of both (nature and
nurture).
"You are born with a predisposition to have a certain personality and
then depending on the culture you are brought up in your personal
situation it becomes active in a particular way."
The study research was jointly funded by the National Health and Medical
Research Council and the US National Institutes of Health.
© 2008 AAP
