Testosterone therapy in trans men results in shifts in the neural processing of emotion, study finds

Most people would agree that men and women experience emotions differently, due to a combination of brain structure, hormones, and socialization. This leads to the question, when a transgender person undergoes gender-affirming care, does their emotional processing change? A study published in Psychoneuroendocrinology suggests that hormone therapy can change emotional perception in transgender individuals.

Many people who identify as transgender seek out gender-affirming treatments such as hormone therapy and surgery to help their body feel like it matches their gender identity. Hormone therapy can change more than just a person’s body, also having significant effects on the brain. Sex hormones have been thought to be associated with gender differences in body perception, self-referential processing, language processing, and basic emotion perception.

Despite this, the research on how the brain changes during hormone therapy has been lacking. This study seeks to bridge that gap in research and explore how hormone therapy can affect emotional perception.

Meltem Kiyar and colleagues utilized 26 transgender men, 29 cisgender men, and 30 cisgender women to serve as their sample. Data collection occurred in Belgium. Data was collected at baseline and 6 to 10 months later. Participants were age matched, but their educational levels varied. A clinician administered a neuropsychiatric interview before session 1.

Participants completed questionnaires on anxiety, stress, depression, and sexual orientation. Trans men began receiving long lasting testosterone injections every 12 weeks after the first session and hormone levels were monitored.

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All participants underwent an experimental emotional processing task while undergoing an MRI. The task included faces that represented neutral, happy, angry, and surprised expressions that were grey scaled, had the hair removed, or made to look more agender.

Results showed that cisgender men and women differed in that cisgender men showed lower neural activity when they had higher testosterone, and cisgender women showed higher neural activity when they had higher levels of testosterone.

The researchers found that the neural processing of emotions from session 1 to session 2 was significantly different for trans men, while it remained stable for cis men and women. At timepoint 1, trans men showed neural activity similar to cisgender women, while after hormone therapy, they showed neural activity similar to cisgender men.

“A clear effect of testosterone administration on affective neurocircuitry was present in [trans men] after only 6–10 months of [gender-affirming hormone therapy]. Specifically, in the bilateral amygdala and the [anterior cingulate cortex], neural patterns of processing emotions shifted from a sex-assigned at birth to a gender identity pattern in [trans men] after initiating [gender-affirming hormone therapy],” the researchers said.

This was consistent for positive, negative, and ambiguous emotional stimuli.

“This study provides further evidence on how testosterone affects affective neurocircuitry when processing positive, negative and ambiguous emotions and may contribute to our understanding of emotion perception in the brain,” the researchers added.

This study took interesting and important steps into better understanding how hormone therapy can affect emotional processing. Despite this, there are limitations to note. One such limitation is that this study did not include trans women, so we cannot extrapolate that estrogen would show similar effects. Additionally, timepoint 2 ranged from 6 to 10 months because of COVID-19, which is less consistent. Lastly, other important factors, such as menstruation, were not taken into consideration.

The study, “Gender-affirming hormonal treatment changes neural processing of emotions in trans men: An fMRI study“, was authored by