You are willfully ignorant. There have been studies with fantastic sample sizes and controls. More than you expect.
>Brain activation-based sexual orientation in female-to-male transsexuals.
>Kisspeptin Expression in the Human Infundibular Nucleus in Relation to Sex, Gender Identity, and Sexual Orientation.
>Neuroimaging studies in people with gender incongruence.
>Anatomical and Functional Findings in Female-to-Male Transsexuals: Testing a New Hypothesis.
>Gender dysphoria "cured" by status epilepticus.
>Neural Correlates of Psychosis and Gender Dysphoria in an Adult Male.
>Regional volumes and spatial volumetric distribution of gray matter in the gender dysphoric brain.
>The transsexual brain - A review of findings on the neural basis of transsexualism.
>Hypothalamic response to the chemo-signal androstadienone in gender dysphoric children and adolescents
>Neural network of body representation differs between transsexuals and cissexuals.
>White matter microstructure in transsexuals and controls investigated by diffusion tensor imaging.
>Brain Signature Characterizing the Body-Brain-Mind Axis of Transsexuals
>Cortical thickness in untreated transsexuals.
>Sex dimorphism of the brain in male-to-female transsexuals.
>The microstructure of white matter in male to female transsexuals before cross-sex hormonal treatment. A DTI study
>White matter microstructure in female to male transsexuals before cross-sex hormonal treatment. A diffusion tensor imaging study.
>Neuroimaging differences in spatial cognition between men and male-to-female transsexuals before and during hormone therapy.
>A sex difference in the hypothalamic uncinate nucleus: relationship to gender identity
>Male-to-female transsexuals show sex-atypical hypothalamus activation when smelling odorous steroids.
>Male-to-Female Transsexuals Have Female Neuron Numbers in a Limbic Nucleus
>A sex difference in the human brain and its relation to transsexuality
