Understanding one’s identity is a deeply personal journey shaped by the interplay between biology and the environment. Nowhere is this journey more complex than in understanding the “brain sex” or the “gendered brain,” which refers to cases where an individual’s assigned sex at birth does not align with their gender identity. The allure of the “gendered brain” persists in both scientific and public discourse, framing the dynamic relationship between biology, environment, and culture.
Beyond the binary of gender and sex
“Gender identity is rooted in our brains,” postulates Antonio Guillamón Fernandez, a psychobiologist and professor from the National University of Distance Education in Spain. Probing into the link between gender identity and neuroscience, his research addresses the enduring question of how the brain’s structure contributes to the emergence and experience of one’s gender.
For most people, their biological sex or genital characteristics align with their internal sense of self, serving as tangible biological markers. However, Fernandez estimates that between 0.005 percent and 0.014 percent of individuals experience a mismatch, which means that in a city of one million people, only about 50 to 140 people would be affected.
This incongruence can manifest as gender dysphoria (GD), a condition often characterized by psychological distress, symptoms of depression, and a rejection of one’s genitalia. Because self-perception is closely tied to bodily awareness, Fernandez’s study shows how variations in the brain—particularly in the cerebral cortex—may underpin this condition.
Importantly, not all transgender individuals experience GD. Fernandez clarifies that the term “transgender” encompasses a broad spectrum of identities that challenge the traditional male-female binary framework, including agender, genderfluid, and bigender. It is not limited to trans individuals who choose to undergo gender reassignment surgery.
Fernandez further stresses that GD is not a disease, but rather a different process of sexual differentiation that occurs in the brain. This wide range of experiences further highlight how gender is not only a product of biology but also psychology and culture.
The brain and the body
Using brain imaging techniques like magnetic resonance imaging, Fernandez proposes the existence of four distinct phenotypes, or observable traits of the brain: those of cisgender men, cisgender women, transgender men, and transgender women.
In the brain regions untouched by medical intervention, these phenotypes often remain consistent with their original assigned gender. But even within these groups, variation is the norm. The brains of transgender women, for example, “are not fully feminized.” As Fernandez observes, “Certain brain regions exhibit female-typical characteristics, others remain male-typical, and some appear demasculinized.” Similar patterns are evident in the brains of transgender men.
This implies that gender identity is a mosaic of characteristics. Rather than reinforcing a rigid binary, neuroscience points toward a spectrum in which transgender brains may blend, overlap, or diverge from conventional norms to reflect their lived identities.
Medical interventions build on this understanding by reducing gender incongruence and alleviating the associated dysphoria. These include hormone-replacement therapy (HRT) and gender-affirming surgery. For instance, changes induced by HRT include an increase in the thickness of the cortex in transgender males and the opposite for transgender females.
“These changes do not imply an increase or decrease in the number of neurons, but rather reflect alterations in water metabolism that affect the size of certain brain cells known as astrocytes,” Fernandez adds. Much like scaffolding, astrocytes are star-shaped cells that support the formation of the brain and nervous system. HRT causes these scaffolds to subtly change shape, nudging the brain to adjust to an individual’s new and desired gender identity.
Dimensions of gender identity research
Insights into the neurological basis of gender dysphoria are growing. However, it remains difficult to make progress, as the neuroimaging techniques utilized by his team limit their studies to ones of a correlational nature. Furthermore, Fernandez’s team is one of the few globally using molecular genetics to study the neurobiological basis of gender identity.
Unfortunately, progress in the understanding of transgender people faces significant barriers due to the politicization of the field. A US-based neurobiology professor stated that scientists have come under attack for researching transgenderism and are discouraged from pursuing this line of study. Fernandez also adds that social stigmas and data collection further hinder progress, particularly due to societal discrimination against transgender people.
Access to gender-affirming care is still restricted in many nations, including the Philippines. Locally, transgender people are prohibited from changing their names, gender markers, or school uniforms to ones that align with their preferred gender identity, preventing them from living as who they are.
In the US, these challenges have been exacerbated by the Trump administration, whose anti-LGBTQ+ and diversity, equity, and inclusion initiatives have led to cuts in research funding, including the loss of grants for research into transgender health.
Historically, findings about sex and gender differences in the brain have been weaponized to reinforce stereotypes or justify unequal treatment. Today, feminists scrutinize how gender biases and stereotypes in research are embedded with biases, questioning whether they perpetuate outdated gender norms or expand understanding.
Even the field of neuroscience has been influenced by sexism and gender bias, which hinder research on female and transgender individuals. The predominance of male neuroscientists has contributed to the neglect of studying female-specific brains. As a result, questions relevant to women or gender minorities are often overlooked or undervalued, limiting the depth of neuroscientific understanding of gender.
Confronting these biases will allow people to make sense of their gender identity. While these studies may not provide all the answers, they do offer valuable clues to process the concepts of sex and gender. They also affirm transgender identities as something real and valid, rooted in biology as well as personal truth. More support is needed to encourage this type of work. Because when transgender research is stifled by politics and stigma, people are kept further away from understanding who they truly are.
This article was published in The LaSallian‘s June 2025 issue. To read more, visit bit.ly/TLSJune2025.
