Researchers out of Brazil have noticed structural differences in a specific region of the brains of transgender women, according to a study published in Scientific Reports.

The authors examined MRI results of 80 individuals between the ages of 18 and 49, looking specifically for differences in gray and white matter volume. The group included 20 individuals from four different groups: cisgender women, cisgender women, transgender women who have never used hormones and transgender women who have used hormones for at least one year.

Overall, the authors found variations in the volume of the insula, the part of the brain that plays a key role in a person’s self-awareness, in both groups of transgender women. The insula in the transgender women was “reduced” compared to cisgender women. This does not, the authors emphasized, mean that a transgender woman's insula has fewer nerve cells.

“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,” first author Giancarlo Spizzirri, PhD, University of São Paulo Medical School (FMUSP) in São Paulo, Brazil, said in a prepared statement.

Carmita Abdo, MD, PhD, coordinator of the Sexuality Research Program at the Psychiatry Institute of Hospital das Clinicas in São Paulo, Brazil, served as the study’s principal investigator. Abdo said in the statement that this study shows that transgender “doesn’t just refer to different kinds of behavior that people develop.”

“The evidence is building up that it's not a matter of ideology,” Abdo said. “Our own research based on MRI scans points to a detectable structural basis.”

Since this finding was in transgender women who have received hormone treatment and those who have not, the authors noted that such treatments should not be considered a possible cause of the variations.