Transgender Identity: An Investigation for a Biological Mechanism

By Rachel Sebastian | UTS Staff Writer | SQ Online (2015-16)


Ask any UC San Diego student who Caitlyn Jenner is, and most people will know the answer. The media has highlighted Caitlyn Jenner ever since she announced her identity as a woman this year. This spotlight on Jenner has helped bring attention to differences in gender identity.

A significant change regarding gender identity has occurred in the University of California system this year. Beginning this fall,  students applying to a University of California school have the opportunity to choose among 6 gender identities: male, female, transgender male, transgender female, gender non-conforming and different identity. With the broadening of choices previously limited to male or female, the University of California aims to gain a better understanding of the student population.

Changes like that of the University of California application tied with Jenner’s spotlight in the media have stimulated debate over the relationship between physical sex and gender identity. Physical sex refers to the biological status of being male or female and is determined by physical characteristics, such as reproductive anatomy and sex hormones, and chromosomes. In comparison, gender identity is the gender a person identifies with, and encompasses the behavior, roles, and activities attributed to certain sexes. If one’s physical sex and gender identity are the same, the term one might use to describe themselves is cisgender. If one’s physical sex from birth is different from one’s gender identity, the term one might use to describe themselves is transgender.

By investigating gender determination and the brain, biology researchers are trying to answer Brain_s_genderthis hot question of today’s changing society: Does gender identity have a biological basis independent of one’s chromosomes or physical anatomy?

Studies suggest a possible neurological basis for gender identity separate from physical sex. A study from 2014 by brain researcher Georg S. Kranz of the Medical University of Vienna suggests that the gender identity of a human being could be identified in the microstructure of the brain’s white matter. The method Kranz and other researchers used was diffusion-based magnetic resonance tomography, a method that reveals brain structure by observing the movement of water molecules. By comparing the brains of 23 transgender men and 21 transgender women to those of 22 cisgender men and 23 women, Kranz and other researchers showed significant differences between the microstructures of white matter tracts in cisgender male and female subjects. However, transgender male and female subjects showed an intermediate structure in white matter tracts. The study further detected that these differences in microstructures may be related to the testosterone levels in blood. Rupert Lanzenberger, one of the researchers involved in this study, stated, “These results suggest that the gender identity is reflected in the structure of brain networks which form under the modulating influence of sex hormones in the course of the development of the nervous system.” Could a distinct gender identity be based in differences between the brain’s microstructure? In order to confirm a neurologically-based gender identity, more research needs to be conducted.

Psychologist Kristina Olson of the University of Washington conducted a study in 2014 investigating gender identity by analyzing subtle behavioral cues of 32 transgender children ages 5 to 12 years. By using these implicit measures, Olson could better assess the children’s automatic gender associations and gender identity. Results showed that transgender children identified with their expressed gender rather than their physical sex. The data pattern for both transgender girls and transgender boys showed strong similarities to the data pattern of cisgender girls and cisgender boys, respectively. The results suggest that transgender gender identity in children is a total change in response that contrasts with their physical sex. Though this study needs further investigation, the evidence of a total change in behavior further suggest a possible biologically-based gender identity.

Based on this research, is there a biological mechanism for gender identity separate from physical sex? Whether gender identity is biologically separate from physical sex is a question that cannot be answered definitively yet. However, with the greater publicity for transgender identity from individuals like Jenner, it is likely that more research that focuses on biological mechanisms for gender identity will be conducted. These ongoing studies on gender identity not only offer a promising beginning, but also are feats that celebrate the burgeoning harmony between biology research and gender identity.