From Wikipedia:
Several studies have found a correlation between gender identity and brain structure.[15][16] A first-of-its-kind study by Zhou et al. (1995) found that in the bed nucleus of the stria terminalis (BSTc), a region of the brain known for sex and anxiety responses (and which is affected by prenatal androgens),[17] cadavers of six trans women had female-normal BSTc size, similar to the study's cadavers of cisgender women. While the trans women had undergone hormone therapy, and all but one had undergone sex reassignment surgery, this was accounted for by including cadavers of cisgender men and cisgender women as controls who, for a variety of medical reasons, had experienced hormone reversal. The controls still had sizes typical for their sex, and thus no relationship to post-natal hormone levels (nor to sexual orientation) was found.[18][19] Other post-mortem studies also found brain differences between cisgender and transgender individuals.[20]
As for som of the articles themselves:
* Zhou JN, Hofman MA, Gooren LJ, Swaab DF (November 1995). "A sex difference in the human brain and its relation to transsexuality". Nature (https://pure.knaw.nl/portal/en/publications/a-sex-difference-in-the-human-brain-and-its-relation-to-transsexuality(9da6a0a1-f622-44f3-ac4f-fec297a7c6c2).html)
* Frigerio, Alberto; Ballerini, Lucia; Valdes-Hernandez, Maria (2021). "Structural, Functional, and Metabolic Brain Differences as a Function of Gender Identity or Sexual Orientation: A Systematic Review of the Human Neuroimaging Literature". Archives of Sexual Behavior. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8604863)