US scientists have reportedly found so-called 'gay genes' that may dictate sexuality in men.
Scientists have been searching for a so-called 'gay gene' and studying how sexual orientation is partly biologically determined, the New Scientists reports.
Now, a new study has identified what might be two genes which have an impact on someone's sexuality.
The study, carried out by Alan Sanders and his team at North Shore University, Illinois, compared DNA from 1077 gay and 1231 straight men.
They scanned participants' genomes to look for differences in their DNA sequences to find genes whose variants may link to sexual orientation.
The first gene found, called SLITRK6, sits on chromosome 13 and is an active part of the brain called the diencephalon, the same region of the brain that contains the hypothalamus, a part of the brain which produced hormones involved in sex drive.
Previous studies have shown parts of the hypothalamus are up to 34 per cent larger in gay men, The Telegraph reports. The second gene, called TSHR, is found on chromosome 14 and is mainly active on the thyroid but also the brain. It binds a hormone that stimulates the thyroid, effectively controlling it.
Previous studies have linked thyroid function to sexual orientation in men as more gay men suffer from a genetic condition called Grave's disease, which disrupts TSHR's function.
It causes the thyroid to go into overdrive, accelerating metabolism and resulting in weight-loss. Previous studies suggested that gay men tend to be thinner, possibly as a result of thyroid overdrive.
Neuroscientist Simon LeVay told New Scientist: "This is thought to be a crucial time for sexual differentiation in this part of the brain."
"So this particular finding is a potential link between the neuroanatomy and molecular genetics of sexual orientation."
Research into so-called 'gay genes' is not without controversy. Critics argue that the acceptance of LGBT people should not depend on whether their identity is biologically determined, while some argue that finding genes linked to sexuality could open the door to possible abuse of the technology.