NEUROENDOCRINOLOGY
LETTERS
including
Psychoneuroimmunology, Neuropsychopharmacology,
Reproductive Medicine, Chronobiology
and Human Ethology
ISSN 0172–780X
Is
there a gender difference of somatostatin-receptor density
in the human brain? Robert Pichler (1), Wilhelmine Maschek
(1), Carmen Crespillo (2),
Isabel Esteva (2), Federico Soriguer (2)
(1) Institute of Nuclear Medicine and Endocrinology,
General Hospital Linz, Linz, AUSTRIA
(2) Complejo Hospitalario Carlos Haya, Málaga, SPAIN
Animal
experiments and observations in human brains have convincingly
shown that sexual differentiation not only concerns the genitalia
but also the brain. This has been investigated also in the
light of a possible explanation of a presumed biological aetiology
of transsexuality. The volume of the central subdivision of
the bed nucleus of the stria terminalis, a brain area that
is essential for sexual behaviour, has been reported to be
larger in men than in women. Additionally, the number of somatostatin
expressing neurons in this region was shown to be higher in
men than in women. As neuronal production of somatostatin
is involved the idea is striking whether somatostatin-receptor
density in the cortex of cerebral hemispheres might be related
to gender identity. We investigated in vivo the density of
somatostatin-receptors in selected regions of the human brain
in both sexes by means of receptor scintigraphy.
Basal ganglia tracer uptake of 111-In-Pentreotide was equally
low in both genders at 0,80% +/– 0,26 (related to tracer
uptake of the whole brain layer). Temporal cortex accumulated
at 2,9% +/– 1,1 in men and at 2,3% +/– 0,76 in women.
Frontal brain region had an uptake of 3,0% +/– 1,4 in
male and of 2,5% +/– 1,3 in female. This shows a tendency
in males for relatively augmented uptake indicating higher
somatostatin receptor density in temporal and frontal cerebral
cortex.
* * *
SIR
– Animal experiments and observations in human brains
have convincingly shown that sexual differentiation not only
concerns the genitalia but also the brain. This has been investigated
also in the light of a possible explanation of a presumed
biological aetiology of transsexuality. The volume of the
central subdivision of the bed nucleus of the stria terminalis,
a brain area that is essential for sexual behaviour, has been
reported to be larger in men than in women [1]. Additionally,
the number of somatostatin expressing neurons in this region
was shown to be about 70% higher in men than in women [2,
3]. Meanwhile, female-like structural changes of specific
brain regions were also found in homosexual and transsexual
men [4]. This data marked a pathway for the understanding
of neuroendocrinological sex differences. As neuronal production
of somatostatin is involved, the idea is striking whether
somatostatin-receptor density in the cortex of cerebral hemispheres
might be related to gender identity. We investigated in vivo
the density of somatostatin-receptors in selected regions
of the human brain in both sexes by means of receptor scintigraphy.
We reevaluated the scintigraphic pattern in brain of ten men
and 14 women who had been sent to our institute to practice
Octreo-Scan for calculating an acitivity score on the orbitae
because of Graves’ ophthalmopathy in the years 1997–2000.
Mean age was 47 yr.+/–9 in men and 41 yr.+/–10 in
women. No patient presented any clinical apparent neurological
disease, the serum levels of thyroxin were maintained in the
normal range at time of investigation.
To evaluate somatostatin-receptor status SPECT of the head
was performed with a double-headed rotating gamma camera 2–4
hours after i.v. application of 110 MBq 111-In-Pentreotide.
About five layers of the transversal oblique sections were
added up to cover the basal ganglia region, using PICKER software
provided by the manufacturer. Regions of interest (ROI) were
calculated for basal ganglia, frontal and temporal brain cortex
of the same size (on right and left side). The tracer uptake
of the whole brain layer was measured as well.
All values of brain regions were calculated as a mean of both
sides as marked asymmetry was observed and regions were related
to whole brain layer. Basal ganglia tracer uptake was equally
low in both genders at 0,80%+/–0,26. Temporal cortex
accumulated at 2,9%+/–1,1 in men and at 2,3%+/–0,76
in women. Frontal brain region had an uptake of 3,0%+/–1,4
in male and of 2,5%+/–1,3 in female. By Fisher’s
t-test no statistical significant difference was found between
both sexes or different cortical regions, probably due to
the small number of persons. Anyhow, there was a tendency
in males for relatively augmented uptake indicating higher
somatostatin receptor density in temporal and frontal cerebral
cortex. To be compared with, sex differences in the distribution
of androgen receptors in human brain structures have already
been reported [5]. Further investigation e.g. by means of
immune-histochemistry or PCR of cerebral cortex is encouraged
to clarify a possible gender difference on the axis of somatostatin
and its receptor or receptor subtypes in human brain.
REFERENCES
1 Zhou JN, Hofman MA, Gooren LJ, Swaab DF. A sex difference
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2 Kruijver FP, Zhou JN, Pool CW, Hofman MA, Gooren LJG, Swaab
DF. Male-to-female transsexuals have female neuron numbers
in a limbic nucleus. J Clin Endocrinol Metab 2000; 85:2034–2041.
3 Chung WC, De Vries GJ, Swaab DF. Sexual differentiation
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into adulthood. J Neurosci 2002; 22:1027–1033.
4 Dörner G, Götz F, Rohde W, Plagemann A, Lindner
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