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. 2009 Jul 15;46(4):904-7.
doi: 10.1016/j.neuroimage.2009.03.048. Epub 2009 Mar 31.

Regional Gray Matter Variation in Male-To-Female Transsexualism

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Free PMC article

Regional Gray Matter Variation in Male-To-Female Transsexualism

Eileen Luders et al. Neuroimage. .
Free PMC article

Abstract

Gender identity-one's sense of being a man or a woman-is a fundamental perception experienced by all individuals that extends beyond biological sex. Yet, what contributes to our sense of gender remains uncertain. Since individuals who identify as transsexual report strong feelings of being the opposite sex and a belief that their sexual characteristics do not reflect their true gender, they constitute an invaluable model to understand the biological underpinnings of gender identity. We analyzed MRI data of 24 male-to-female (MTF) transsexuals not yet treated with cross-sex hormones in order to determine whether gray matter volumes in MTF transsexuals more closely resemble people who share their biological sex (30 control men), or people who share their gender identity (30 control women). Results revealed that regional gray matter variation in MTF transsexuals is more similar to the pattern found in men than in women. However, MTF transsexuals show a significantly larger volume of regional gray matter in the right putamen compared to men. These findings provide new evidence that transsexualism is associated with distinct cerebral pattern, which supports the assumption that brain anatomy plays a role in gender identity.

Figures

Fig. 1
Fig. 1
Analysis of variance (ANOVA) between samples. The color-coded brain maps illustrate the brain regions where gray matter volumes differ significantly between the three groups (MTF transsexuals, males, females), after removing the variance associated with age. Statistical outcomes are corrected for multiple comparisons, using FDR at p<0.001. Shown are clusters exceeding a spatial extent threshold of 123 voxels. The two box plots display the estimated parameters for clusters located in the region of the left and right putamen, where MTF transsexuals (TR) had more gray matter than males (MA) and females (FE).
Fig. 2
Fig. 2
T-tests between samples. The overlay maps on the SPM standard glass brain template (sagittal, axial, and coronal view) illustrate where independent-sample group comparisons revealed significant gray matter volume differences between females and males (Panel A), between females and MTF transsexuals (Panel B), as well as between males and MTF transsexuals (Panel C), after removing the variance associated with age. Panel D depicts the overlay of significance profiles from different sets of comparisons. Findings are significant at p<0.001, FDR-corrected.

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