With respect to MtFs, Hulshoff Pol et al. (
2006) found that before treatment subjects’ brain volume was consistent with their natal sex. Estradiol plus antiandrogen produced a decrease in brain volume “towards female proportions” after 4 months of treatment, a decrease they found to be ten times the average annual decrease in healthy adults. Moreover, the ventricles became larger.
Recently, Zubiaurre-Elorza et al. (
2014) measured cortical thickness and the volume of the brain and cortical and subcortical structures in MtFs. After at least 6 months of treatment, they found a general decrease in all these measurements together with increased ventricle volume. The volumetric analyses showed a significant decrease in the total and cortical gray matter volumes. Subcortical gray matter volume also showed a decrease that was centered in the right thalamus and right pallidum. Consequently, and due to the production of a mechanical vacuum, there was a significant increase in the whole ventricular system. The decrease seen in CTh was also generalized but most strongly affected the cortex in the occipital, temporal, and parietal regions and some areas of the frontal lobes (Fig.
5).
*SNIP*
Contrary to FtMs, the suppression of testosterone in MtFs via antiandrogens would diminish the anabolic tone in brain tissues and induce decreases (Zubiaurre-Elorza et al.,
2014). Moreover, the effect of estradiol administration could also play an additional role via its adverse effects on the brain (Zubiaurre-Elorza et al.,
2014).
Estradiol is selectively cytotoxic to β-endorphin neurons and perhaps other cells. The mechanism involves aromatic hydroxylation of estradiol to catechol estrogens and the production of free radicals in the hypothalamus (Brawer, Beaudet, Desjardins, & Schipper,
1993); the developing human hypothalamus and cerebral cortex can produce catechol estrogens (Fishman, Naftolin, Davies, Ryan, & Petro,
1976).
