Transgender individuals' brains may be structured differently

Scientists from the University of São Paulo Medical School in Brazil have found that individuals who identify as transgender have volumetric difference in their brains and subsequently may interpret body image in various ways.   

According to a recent release from the São Paulo Research Foundation, researchers performed a structural analysis to search for differences in gray and white matter volume based on MRI brain scans of 80 transgender individuals between the ages of 18 and 49. Study participants were also divided into four groups of 20 cisgender women, cisgender men, transgender women who never used hormones and transgender women who had used hormones for at least one year.  

The study, published online Jan. 15 in Scientific Reports, demonstrated notable differences in the volume of the brain's insula in both hemispheres for both groups of transgender women inexplicable by hormone treatment. The insula plays a key role in body image, self-awareness and helps process autonomic control, homeostatic information and visceral sensations within the central nervous system, according to the researchers. 

"There's no such thing as a typically female or male brain," said lead author of the study Giancarlo Spizzirri, PhD, in a prepared statement. "There are slight structural differences, which are far more subtle than the difference in genitals, for example. Brain structures vary greatly among individuals." 

The size of the insula was found to similar in transgender women and cisgender men, but its volume was reduced in transgender women compared to cisgender women, according to study results. Despite these results, researchers asserted that reduced gray matter volume does not infer that the insulas of the transgender and cisgender women contains fewer nerve cells.

"It would be simplistic to make a direct link with transgender, but the detection of a difference in the insula is relevant since trans people have many issues relating to their perception of their own body because they don't identify with the sex assigned at birth, and in addition, they unfortunately suffer discrimination and persecution," said associate researcher Geraldo Busatto, PhD, head of the psychiatric neuroimaging laboratory at University of São Paulo's Medical School general and teaching hospital, Hospital das Clínicas.

Carmita Abdo, lead investigator of the study and coordinator of the Sexuality Research Program at the Psychiatry Institute of Hospital das Clínicas, explained another contribution of the study is it shows transgender "doesn't just refer to different kinds of behavior that people develop," according to the press release.  

"We found that trans people have characteristics that bring them closer to the gender with which they identify and [that] their brains have particularities, suggesting that the differences begin to occur during gestation," the researchers said in the press release. "We hope this study will be replicated with larger samples, but right now, it can be said that the hypothesis of transgender development is supported and merits investigation."