Poster No:
1748
Submission Type:
Abstract Submission
Authors:
Daisy Hu1, Artit Rodkong2, Monika Folkierska-Zukowska1, Malvina Skorska3, Pongpun Saokhieo2, Diana Peragine1, Celina Javier1, Lindsey Thurston1, Sherri Jones4, Taweewat Supintham2, Oranicha Kaewthip2, Kittichai Wantanajittikul2, Suwat Chariyalertsak2, Suwit Saekho2, Doug VanderLaan1
Institutions:
1University of Toronto Mississauga, Mississauga, Ontario, 2Chiang Mai University, Chiang Mai, Chiang Mai, 3University of Toronto St. George, Toronto, Ontario, 4McGill University, Montreal, Quebec
First Author:
Daisy Hu
University of Toronto Mississauga
Mississauga, Ontario
Co-Author(s):
Celina Javier
University of Toronto Mississauga
Mississauga, Ontario
Introduction:
Examining how brain structure relates to sex, sexual orientation, and gender identity, and, in the case of transgender individuals, gender-affirming hormone (GAH) use, can help elucidate factors driving neural variation and has implications for brain health. Sexually and gender-diverse individuals may display shifts in sexually differentiated brain traits, likely influenced by varying hormone exposure during development (Guillamon et al., 2016). In rats and sheep, the sexually dimorphic nucleus of the preoptic area, an anterior hypothalamic structure crucial for sexual behaviour, is larger in males than females, and this difference is hormonally mediated (Houtsmuller et al., 1994; Roselli et al., 2004). Post-mortem, the human homologue (i.e., the third interstitial nucleus of the anterior hypothalamus) was smaller in cisgender and transgender women, as well as gay men, compared with heterosexual men (Byne et al., 2001; Garcia-Falgueras & Swaab, 2008). Recently developed analytic tools allow for examination of the anterior hypothalamus in vivo via structural MRI images (Billot et al., 2020). Thailand, known for its cultural visibility and acceptance of sexual and gender diversity, including recognition of "third sex/gender" identities, offers a unique context for exploring the relationship between sexual and gender diversity and the brain (Skorska et al., 2021). Thus, we examined the size of the anterior hypothalamus in relation to sex, sexual orientation, and gender identity in a sexually and gender diverse Thai sample. We compared individuals assigned male at birth (AMAB): cisgender heterosexual and gay men, transfeminine androphilic sao praphet song (SPS), with and without a history of gender-affirming hormone (GAH) use (GAH+ vs. GAH-; GAH+ included individuals who used anti-androgens, estrogens, and/or progesterone, whereas GAH- group had no history of GAH use); and individuals assigned female at birth (AFAB): cisgender heterosexual and lesbian women, transmasculine gynephilic toms, and dees (feminine, attracted to toms). We hypothesized that the structure would be smaller in groups with feminine gender identity/expression and attracted towards males.
Methods:
A 1.5T Philips Ingenia scanner with a 16-channel head coil was used to collect T1-weighted images (N = 230, 23-31/group). The neural network based HypothalamicSubunits tool in FreeSurfer software was used to segment and derive volumes for five hypothalamic subregions, with our analysis focusing on the anterior region (Billot et al., 2020). We conducted two one-way analyses of covariance (ANCOVA) to examine group differences: one controlling for age and the other controlling for both age and intracranial volume (ICV). Pairwise comparisons were performed using estimated marginal means.
Results:
The ANCOVA controlling for age revealed a main effect of group, F(7, 221) = 3.55, p = .001, η² = .100. Pairwise comparisons showed that heterosexual men and GAH- SPS, who did not differ from each other, had larger anterior hypothalamus volumes than GAH+ SPS, toms, dees, and heterosexual women. Gay men had larger volumes than toms and heterosexual women. The ANCOVA controlling for age and ICV revealed no main effect of group, F(7, 220) = 1.89, p = .072, η² = .056.
Conclusions:
The findings partly support predictions. Heterosexual men had larger anterior hypothalamic volume than heterosexual women. In the GAH+ SPS group, the volume was shifted to resemble that of heterosexual women, while other groups largely aligned with their birth-assigned sex. Thus, GAH use, but not sexual orientation or gender identity, may play a role in anterior hypothalamic volume, consistent with prior findings in transgender women (Konadu et al., 2023). However, the observed differences may be confounded by group differences in ICV. Future research on GAH use and anterior hypothalamic volume, while disentangling the effect of ICV, could provide further insights into the neuroanatomical impacts of hormonal treatments.
Emotion, Motivation and Social Neuroscience:
Sexual Behavior 2
Modeling and Analysis Methods:
Segmentation and Parcellation
Neuroanatomy, Physiology, Metabolism and Neurotransmission:
Subcortical Structures 1
Keywords:
ADULTS
MRI
Segmentation
Sexual Dimorphism
STRUCTURAL MRI
Sub-Cortical
Other - Hypothalamus
1|2Indicates the priority used for review
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Healthy subjects only or patients (note that patient studies may also involve healthy subjects):
Healthy subjects
Was this research conducted in the United States?
No
Were any human subjects research approved by the relevant Institutional Review Board or ethics panel?
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Yes
Were any animal research approved by the relevant IACUC or other animal research panel?
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Not applicable
Please indicate which methods were used in your research:
Structural MRI
For human MRI, what field strength scanner do you use?
1.5T
Which processing packages did you use for your study?
Free Surfer
Provide references using APA citation style.
1. Automated segmentation of the hypothalamus and associated subunits in brain MRI. NeuroImage, 223, 117287.
2. Byne, W., Tobet, S., Mattiace, L. A., Lasco, M. S., Kemether, E., Edgar, M. A., Morgello, S., Buchsbaum, M. S., & Jones, L. B. (2001). The interstitial nuclei of the human anterior hypothalamus: An investigation of variation with sex, sexual orientation, and HIV status. Hormones and Behavior, 40(2), 86–92.
3. Garcia-Falgueras, A., & Swaab, D. F. (2008). A sex difference in the hypothalamic uncinate nucleus: Relationship to gender identity. Brain, 131(12), 3132–3146.
4. Guillamon, A., Junque, C., & Gómez-Gil, E. (2016). A review of the status of brain structure research in transsexualism. Archives of Sexual Behavior, 45(7), 1615–1648.
5. Houtsmuller, E. J., Brand, T., de Jonge, F. H., Joosten, R. N. J. M. A., van de Poll, N. E., & Slob, A. K. (1994). SDN-POA volume, sexual behavior, and partner preference of male rats affected by perinatal treatment with ATD. Physiology & Behavior, 56(3), 535–541.
6. Konadu, M. E., Reed, M. B., Kaufmann, U., Handschuh, P. A., Spurny-Dworak, B., Klöbl, M., Schmidt, C., Godbersen, G. M., Briem, E., Seiger, R., Baldinger-Melich, P., Kranz, G. S., Lanzenberger, R., & Spies, M. (2023). Changes to hypothalamic volume and associated subunits during gender-affirming hormone therapy. Journal of Psychiatry and Neuroscience, 48(5), E369–E375.
7. Roselli, C. E., Larkin, K., Schrunk, J. M., & Stormshak, F. (2004). Sexual partner preference, hypothalamic morphology and aromatase in rams. Physiology & Behavior, 83(2), 233–245.
8. Skorska, M. N., Coome, L. A., Peragine, D. E., Aitken, M., & VanderLaan, D. P. (2021). An anthropometric study of sexual orientation and gender identity in Thailand. Scientific Reports, 11(1), 18432.
No