title: A Review of the Status of Brain Structure Research in Transsexualism.
abstract: The present review focuses on the brain structure of male-to-female (MtF) and female-to-male (FtM) homosexual transsexuals before and after cross-sex hormone treatment as shown by in vivo neuroimaging techniques. Cortical thickness and diffusion tensor imaging studies suggest that the brain of MtFs presents complex mixtures of masculine, feminine, and demasculinized regions, while FtMs show feminine, masculine, and defeminized regions. Consequently, the specific brain phenotypes proposed for MtFs and FtMs differ from those of both heterosexual males and females. These phenotypes have theoretical implications for brain intersexuality, asymmetry, and body perception in transsexuals as well as for Blanchard's hypothesis on sexual orientation in homosexual MtFs. Falling within the aegis of the neurohormonal theory of sex differences, we hypothesize that cortical differences between homosexual MtFs and FtMs and male and female controls are due to differently timed cortical thinning in different regions for each group. Cross-sex hormone studies have reported marked effects of the treatment on MtF and FtM brains. Their results are used to discuss the early postmortem histological studies of the MtF brain.
authors.affiliation: Departamento de Psicobiología, Universidad Nacional de Educación a Distancia, c/Juand del Rosal, 10, 28040, Madrid, Spain. aguillamon@psi.uned.es.|Academia de Psicología de España, Madrid, Spain. aguillamon@psi.uned.es.
authors.forename: Antonio
authors.initials: A
authors.lastname: Guillamon
authors.affiliation: Departamento de Psiquiatría y Psicobiología Clínica, Universidad de Barcelona, Barcelona, Spain.|Institute of Biomedical Research August Pi i Sunyer, Barcelona, Spain.
authors.forename: Carme
authors.initials: C
authors.lastname: Junque
authors.affiliation: Institute of Biomedical Research August Pi i Sunyer, Barcelona, Spain.|Unidad de Identidad de Género, Hospital Clinic, Barcelona, Spain.
authors.forename: Esther
authors.initials: E
authors.lastname: Gómez-Gil
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D035843:Biomedical Research; D001921:Brain / Q000000981:diagnostic imaging*; D002648:Child; D056324:Diffusion Tensor Imaging; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D014189:Transsexualism / Q000000981:diagnostic imaging*; D055815:Young Adult
keywords: Cross-sex hormone treatment; Gender dysphoria; Gender identity; Magnetic resonance imaging; Sex differences; Transsexualism