Biological explanations

• Brain sex theory

  • Incongruence between genital development (1-2 months) and BSTc development (4-9 months)
  • Zhou et al. - BTSc volume; MTF trans in female range
  • Krujvers - BSTc neuronal number; same MTF in female range
  • Therefore, incongruence in biological development
• Genetic basis of gender dysphoria

  • Coolidge et al. - 157 twin pairs, suggested 62% could be accounted for by genetic variance
  • Heylens et al. found 9 (39%) of their MZ twins were concordant for GD, 0 of the DZ were