>>79913324http://sindromebenjamin.tripod.com/sitebuildercontent/sitebuilderfiles/brainsex1.pdf>ABSTRACT>Transsexuals experience themselves as being of the opposite sex,despite having the biological characteristics of one sex. A crucial
question resulting from a previous brain study in male-to-female
transsexuals was whether the reported difference according to gender
identity in the central part of the bed nucleus of the stria terminalis
(BSTc) was based on a neuronal difference in the BSTc itself or just
a reflection of a difference in vasoactive intestinal polypeptide innervation
from the amygdala, which was used as a marker. Therefore, we
determined in 42 subjects the number of somatostatin-expressing
neurons in the BSTc in relation to sex, sexual orientation, gender
identity, and past or present hormonal status. Regardless of sexual
orientation, men had almost twice as many somatostatin neurons as
women (P , 0.006). The number of neurons in the BSTc of maleto-female
transsexuals was similar to that of the females (P 5 0.83).
In contrast, the neuron number of a female-to-male transsexual was
found to be in the male range. Hormone treatment or sex hormone
level variations in adulthood did not seem to have influenced BSTc
neuron numbers. The present findings of somatostatin neuronal sex
differences in the BSTc and its sex reversal in the transsexual brain
clearly support the paradigm that in transsexuals sexual differentiation
of the brain and genitals may go into opposite directions and
point to a neurobiological basis of gender identity disorder. (J Clin
Endocrinol Metab 85: 2034–2041, 2000)
