title: White matter microstructure in female to male transsexuals before cross-sex hormonal treatment. A diffusion tensor imaging study.
abstract: BACKGROUND
  Some gray and white matter regions of the brain are sexually dimorphic. The best MRI technique for identifying subtle differences in white matter is diffusion tensor imaging (DTI). The purpose of this paper is to investigate whether white matter patterns in female to male (FtM) transsexuals before commencing cross-sex hormone treatment are more similar to that of their biological sex or to that of their gender identity.
  
  
  METHODS
  DTI was performed in 18 FtM transsexuals and 24 male and 19 female heterosexual controls scanned with a 3 T Trio Tim Magneton. Fractional anisotropy (FA) was performed on white matter fibers of the whole brain, which was spatially analyzed using Tract-Based Spatial Statistics.
  
  
  RESULTS
  In controls, males have significantly higher FA values than females in the medial and posterior parts of the right superior longitudinal fasciculus (SLF), the forceps minor, and the corticospinal tract. Compared to control females, FtM showed higher FA values in posterior part of the right SLF, the forceps minor and corticospinal tract. Compared to control males, FtM showed only lower FA values in the corticospinal tract.
  
  
  CONCLUSIONS
  Our results show that the white matter microstructure pattern in untreated FtM transsexuals is closer to the pattern of subjects who share their gender identity (males) than those who share their biological sex (females). Our results provide evidence for an inherent difference in the brain structure of FtM transsexuals.
authors.affiliation: Clinical Institute of Neuroscience, Hospital Clinic i Provincial, Barcelona, Spain.
authors.forename: Giuseppina
authors.initials: G
authors.lastname: Rametti
authors.forename: Beatriz
authors.initials: B
authors.lastname: Carrillo
authors.forename: Esther
authors.initials: E
authors.lastname: Gómez-Gil
authors.forename: Carme
authors.initials: C
authors.lastname: Junque
authors.forename: Santiago
authors.initials: S
authors.lastname: Segovia
authors.forename: Ángel
authors.initials: Á
authors.lastname: Gomez
authors.forename: Antonio
authors.initials: A
authors.lastname: Guillamon
mesh_terms: D000293:Adolescent; D000328:Adult; D001921:Brain / Q000473:pathology* / Q000503:physiopathology; D001931:Brain Mapping; D056324:Diffusion Tensor Imaging; D005260:Female; D006801:Humans; D008297:Male; D009413:Nerve Fibers, Myelinated / Q000473:pathology*; D012727:Sex Characteristics; D014189:Transsexualism / Q000473:pathology*; D055815:Young Adult