Biological Findings on Being Transgender

It is critical to note that medical transitioning is not required for someone to be transgender. Neither is the experience of gender dysphoria. It's also important to know that differences in brain structure or neurological processes do not mean that someone has a flaw or disability. We all vary in terms of brain composition and functioning to a certain extent. Nothing on this page is intended to imply such a disability but instead to show how there is a biological basis for many transgender experiences. 

 

Numerous studies have been conducted on transgender people, examining our bodies prior to any form of Gender Affirming Hormone Therapy. The following studies have indicated that there are notable differences that have been measured for many transgender people and that often there are measurable differences between a transgender person and what would be expected for their gender assigned at birth. 

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These studies help reinforce the importance of acknowledging gender dysphoria and gender identity itself as a something with an actual basis in biology and neuroscience. 

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The study "The Neuroanatomy of Transgender Identity: Mega-Analytic Findings from the ENIGMA Transgender Persons Working Group" (2021) in the Journal of Sexual Medicine examined brain patterns of at least 800 participants and found that Transgender women fell into three categories: those closely matching their gender identity, those more closely matching their sex assigned at birth, and those who fell somewhere in between. They also observed that while transgender men had fewer shifts in brain structure compared to their gender assigned at birth, there were still notable shifts (p. 1126). 

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Similarly, "A Review of the Status of Brain Structure Research in Transsexualism" (2016) found that untreated transgender people (both male and female) had brain phenotypes that differed from those expected in their gender assigned at birth (p. 1643). "Neuroimaging Insights into Transgender and Gender Nonconforming Youth: A Scoping Review" (2025) more recently reaffirmed these findings by providing evidence that the brain includes structures specifically related to gender-identity (p. 8). Similarly, a 2022 article by Julie Bakker found deviations in gray matter volume compared to transgender persons' sex assigned at birth. 

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In the article "What Has Sex Got to Do With It? The Role of Hormones in the Transgender Brain" (2019), authors examined brain structures prior to Gender Affirming Hormone Therapy (GAHT) and after GAHT. The researchers noted that transgender men had brain structures (the third ventricle and nucleus accumbens) consistent with cisgender men (p. 27). They also found higher testosterone index values in transgender men (prior to GAHT) than would be expected in cisgender women (p. 30). 

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These findings have been reinforced by other neuroimaging studies. Julie Bakker (2024) found detected differences in brain function, white matter microstructure, and functional connectivity patterns for transgender people (compared to what is expected for their sex assigned at birth) (p. 8). Additionally, a 2022 study "Brain Sex in Transgender Women is Shifted towards Gender Identity" found that transgender women who had never undergone hormone therapy had brains markedly different from those of cisgender men, closer to those of cisgender women (p. 4). 

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The biological evidence is found in numerous studies locating different ways that biology may determine gender identity. The article "Androgen Receptor Repeat Length Polymorphism Associated with Male-to-Female Transsexualism" (2009) was a genetic study on transgender women which found a significant lengthening of the AR gene. The authors noted that this may result in less effective testosterone signalling in early development (p. 4). 

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