The new study was conducted by researchers from the Hudson Institute of Medical Research in Australia and published in The Journal of Clinical Endocrinology & Metabolism. Using the results of a 15-year long project to build a DNA database of transgender women, they analyzed the data from 380 transgender woman compared to a control group comprised of 344 cisgender males. The team investigated 12 functional genetic variants and found four showing significant differences in transgender women that involve genes that regulate the sex hormones estrogen and androgen.
The team hypothesizes that these genetic differences may alter the levels of sex hormones that determine gender identity in the developing brain.
“We know sex hormones like androgens and estrogens have really powerful effects on behavior. But we don’t know if they have effects on gender identity. This points to a role,” says Professor Vincent Harley, the study’s senior author to the Sydney Morning Herald. “We have found a few weak contributors, and there are likely to be very many other genes involved, but these are some small glimpses into the genetics of gender identity that are emerging.”
The results of the study contribute further to recent findings that are showing there is a biological basis to the origins of gender identity. Back in March, a team from Augusta University presented a study that found 20 genetic variants in both transgender males and females that were related to developmental sex hormones and gender identity. The study is still pending peer review. Another study in March by the University of São Paulo's Medical School used MRI technology to show a structural basis in the brains of transgender people that matched the gender in which they identified.
There is also an ongoing study being conducted by a consortium of five research institutions in both Europe and the United States that includes Vanderbilt University Medical Center, George Washington University and Boston Children's Hospital. In this study, they are looking at the DNA of 10,000 subjects (3,000 of which are transgender) to determine the role the human genome plays in gender identity.