Neural mechanisms underlying sexual arousal in connection with sexual hormone levels: a comparative study of the postoperative male-to-female transsexuals and premenopausal and menopausal women.

This study compared the brain activation patterns associated with visual sexual arousal in connection with sexual hormone levels in postoperative male-to-female (MTF) transsexuals and normal premenopausal and menopausal women using 3.0 T functional MRI. A total of 30 volunteers including 10 premenopausal women, 10 menopausal women, and 10 postoperative MTF transsexuals who had undergone sex reassignment surgery participated in this study. Brain activity was measured while viewing erotic male and female nude pictures. The free testosterone and estradiol levels of the postoperative MTF transsexuals were not in the normal range seen in normal premenopausal women, but were in range seen in menopausal women. The postoperative MTF transsexuals showed significantly higher activities in the hippocampus, parahippocampal gyrus, amygdala, putamen, globus pallidus, thalamus, and head of caudate nucleus in response to erotic male nude pictures in contrast to female pictures (P<0.005). The predominant activation areas observed in the postoperative MTF transsexuals in contrast to the menopausal women when viewing male nude pictures included the insula, hippocampus, thalamus, and putamen (P<0.005). Similar to the postoperative MTF transsexuals, the premenopausal women showed significantly higher activities than menopausal women in the insula, hippocampus, thalamus, and parahippocampal gyrus (P<0.005). This study revealed that the brain activation patterns associated with visual sexual arousal in postoperative MTF transsexuals are similar to those in premenopausal women, although the sexual hormone levels in the postoperative MTF transsexuals are in the average range of those in menopausal women.