Following this line of thought, Cantor (
2011,
2012, but also see Italiano,
2012) has recently suggested that Blanchard’s predictions have been fulfilled in two independent structural neuroimaging studies. Specifically, Savic and Arver (
2011) using VBM on the cortex of untreated nonhomosexual MtFs and another study using DTI in homosexual MtFs (Rametti et al.,
2011b) illustrate the predictions. Cantor seems to be right. Nonhomosexual MtFs present differences with heterosexual males in structures that are not sexually dimorphic (Savic & Arver,
2011), while homosexual MtFs (as well as homosexual FtMs) show differences with respect to male and female controls in a series of brain fascicles (Rametti et al.,
2011a,
2011b). If other VBM and CTh studies on the cortex of homosexual MtFs are added (Simon et al.,
2013; Zubiaurre-Elorza et al.,
2013), there is a more substantial number of untreated homosexual MtFs and FtMs that fulfill Blanchard’s prediction but still only one study on nonhomosexual MtFs; to fully confirm the hypothesis, more independent studies on nonhomosexual MtFs are needed. A much better verification of the hypothesis could be supplied by a specifically designed study including homosexual and nonhomosexual MtFs.
Finally, for Blanchard, MtF and FtM homosexual transsexuality is an extreme expression of homosexuality. He considered the following continuum: homosexual → gender dysphoric homosexual → transsexual homosexual (Blanchard, Clemmensen, & Steiner,
1987). Later, Blanchard also hypothesized that homosexual transsexuals should show differences in sexually dimorphic brain structures (Blanchard,
2008). Thus, from Blanchard’s view, there would be no brain differences between homosexual transsexuals and homosexual persons. This hypothesis has not been directly tested yet. However, there are two studies in the literature with respect to cortical thickness that, taken cautiously, may approach Blanchard’s hypothesis on the relationship between transsexuality and homosexuality.
