The Journal of Clinical Endocrinology &
Metabolism, May 2000, p. 2034-2041
Copyright 2000, The Endocrine Society Vol. 85, No. 5
- Male-to-Female Transsexuals Have Female Neuron Numbers
in a Limbic Nucleus
- Frank P. M. Kruijver, Jiang-Ning Zhou, Chris
W. Pool, Michel A. Hofman,
Louis J. G. Gooren, and Dick F. Swaab
-
- Graduate School Neurosciences Amsterdam (F.P.M.K.,
J.-N.Z., C.W.P., M.A.H., D.F.S.), Netherlands Institute for Brain
Research, 1105 AZ Amsterdam ZO, The Netherlands; Department of
Endocrinology (L.J.G.G.),
Free University Hospital, 1007 MB Amsterdam, The Netherlands;
and Anhui Geriatric Institute (J.-N.Z.), The First Affiliated
Hospital of Anhui Medical University, Hefei, Anhui, 230032 China
-
- Address all correspondence and requests for
reprints to: Frank P. M. Kruijver, M.D., or Prof. Dick F. Swaab,
M.D., Ph.D., Graduate School Neurosciences Amsterdam, Netherlands
Institute for Brain Research, Meibergdreef 33, 1105 AZ Amsterdam
ZO, The Netherlands. E-mail: F.Kruijver@nih.knaw.nl.
-
- 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 male-to-female transsexuals was similar to that of the
females (P =3D 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.
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