(001) Brain Activation Patterns Associated with Visually Evoked Sexual Arousal in Female-To-Male Transgender Individuals

Cross-sex hormones in female-to-male (FtM) transgender individuals play a crucial role in brain plasticity. Brain activity associated with sexual arousal in FtM transgenders receiving cross-sex hormones is poorly understood. This study aimed to compare brain activation patterns associated with sexual arousal between FtM transgenders and premenopausal women using a 3.0 Tesla functional magnetic resonance imaging (fMRI). This study included 13 FtM transgenders (mean age: 43.2±6.4 years) and 13 premenopausal women (mean age: 41.5 ± 8.3 years). The FtM transgender individuals, who have had sex-reassignment surgery, received testosterone supplementary therapy. Sexual orientation was evaluated using the Kinsey sexuality rating scale (0 = exclusively heterosexual; 6 = exclusively homosexual). Serum sex hormones were measured, including free testosterone (free-T), estradiol (E2), follicle-stimulating, and luteinizing hormones. Visual sexual stimulation began with a 30-s cross fixation (rest condition), followed by a 30-s natural documentary (neutral condition), 540-s erotic video (sexual activation condition), then a 30-s cross fixation (rest condition). The fMRI data were post-processed using SPM8 software. The average rating of the Kinsey scale in the FtM transgenders was 5.6 ± 0.5, indicating their sexual orientation falls within the category of homosexual. The FtM transgenders showed significant increases in the free-T levels (18.8±18.9 pg/mL vs. 0.4±0.4 pg/mL, p < 0.001) and significant decreases in the E2 levels (45.4±32.0 pg/mL vs. 279.2±247.3 pg/mL, p = 0.001) compared with premenopausal women. The brain areas with significantly higher activities during visual sexual stimuli in the FtM transgenders compared with premenopausal women included the superior parietal lobule, middle occipital gyrus, and superior frontal gyrus (p < 0.001). This study illustrates the specific brain activation patterns associated with sexual arousal in female-to-male (FtM) transgenders. These findings could contribute to our understanding of the neural mechanisms associated with sexual arousal in relation to the levels of sexual hormones in FtM transgenders. This research was supported by grants from the National Research Foundation funded by the government (MSIT; 2022R1A2C2007809, 2021R1C1C2011748). No.