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| Transsexual gene link identified | |
| (about 11 hours later) | |
| Australian researchers have identified a significant link between a gene involved in testosterone action and male-to-female transsexualism. | |
| DNA analysis from 112 male-to-female transsexual volunteers showed they were more likely to have a longer version of the androgen receptor gene. | DNA analysis from 112 male-to-female transsexual volunteers showed they were more likely to have a longer version of the androgen receptor gene. |
| The genetic difference may cause weaker testosterone signals, the team reported in Biological Psychiatry. | The genetic difference may cause weaker testosterone signals, the team reported in Biological Psychiatry. |
| However, other genes are also likely to play a part, they stressed. | However, other genes are also likely to play a part, they stressed. |
| Increasingly, biological factors are being implicated in gender identity. | Increasingly, biological factors are being implicated in 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 Professor Vincent Harley, researcher | There is a social stigma that transsexualism is simply a lifestyle choice, however our findings support a biological basis of how gender identity develops Professor Vincent Harley, researcher |
| One study has shown that certain brain structures in male-to-female transsexual people are more "female like". | One study has shown that certain brain structures in male-to-female transsexual people are more "female like". |
| In the latest study, researchers looked for 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. | In the latest study, researchers looked for 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. |
| Comparison of the DNA from the male to female transsexual participants with 258 controls showed a significant link with a long version of the androgen receptor gene and transsexualism. | Comparison of the DNA from the male to female transsexual participants with 258 controls showed a significant link with a long version of the androgen receptor gene and transsexualism. |
| Testosterone | Testosterone |
| It is known that longer versions of the androgen receptor gene are associated with less efficient testosterone signalling. | It is known that longer versions of the androgen receptor gene are associated with less efficient testosterone signalling. |
| This reduced action of the male sex hormone may have an effect on gender development in the womb, the researchers speculated. | This reduced action of the male sex hormone may have an effect on gender development in the womb, the researchers speculated. |
| "We think that these genetic differences might reduce testosterone action and under masculinise the brain during foetal development," said researcher Lauren Hare from Prince Henry's Institute of Medical Research. | "We think that these genetic differences might reduce testosterone action and under masculinise the brain during foetal development," said researcher Lauren Hare from Prince Henry's Institute of Medical Research. |
| Co-author Professor Vincent Harley added: "There is a social stigma that transsexualism is simply a lifestyle choice, however our findings support a biological basis of how gender identity develops." | Co-author Professor Vincent Harley added: "There is a social stigma that transsexualism is simply a lifestyle choice, however our findings support a biological basis of how gender identity develops." |
| Although this is the largest genetic study of transsexualism to date, the researchers now plan to see if the results can be replicated in a larger population. | Although this is the largest genetic study of transsexualism to date, the researchers now plan to see if the results can be replicated in a larger population. |
| Terry Reed from the Gender Identity Research and Education Society said she was convinced of a biological basis to transsexualism. | Terry Reed from the Gender Identity Research and Education Society said she was convinced of a biological basis to transsexualism. |
| "This study appears to reinforce earlier studies which have indicated that, in some trans people, there may be a genetic trigger to the development of an atypical gender identity. | "This study appears to reinforce earlier studies which have indicated that, in some trans people, there may be a genetic trigger to the development of an atypical gender identity. |
| "However, it may be just one of several routes and, although it seems extremely likely that a biological element will always be present in the aetiology of transsexualism, it's unlikely that developmental pathways will be the same in all individuals." | "However, it may be just one of several routes and, although it seems extremely likely that a biological element will always be present in the aetiology of transsexualism, it's unlikely that developmental pathways will be the same in all individuals." |