Transcript SEXUAL DIMORPHISMS IN HUMAN BRAIN (Swaab et al

SEXUAL DIMORPHISMS
IN
HUMAN BRAIN
(Swaab et al., Hormones and Behavior, 2001
Problems to study humans
• Use of bioptic material
• No possibility of having homogenous groups
• Difficulties to find the clinical history
• Presence of brain pathologies
• The legal period for autopsy is depending by the local
laws (in Italy 48 hours postmortem, in Netherlands 8
hours)
General features
Woman
Man
• Weight: 1171 gr
• Weight: 1308 gr
• 19 mil of neurons
• 23 mil of neurons
• Higher cerebral
metabolism
• Higher cerebral volume in
childrens
• Higher linguistic
capacities
• Higher serotonin
synthesis (+53%)
Sexual dimorphism according to Swaab
Sexual dimorphism according to Gorsky
Sexually dimorphic nuclei
of the human hypothalamus
Differences in volume
Allen et al., 1989
Swaab and Fliers, 1985
Comparison
SDN-POA
• volume 2.2 higher in man
than in woman
• Cell number about 2
times higher in man
INAH
• INAH1 8% > in HIV+
• INAH2 volume 2 times higher
in man
• INAH3 volume 3 times in man
• INAH4 no dimorphism
Development and sexual differentiation of the SDN-POA
Cell number reach a peak value around 2-4 years postnatally, after which a sexual
differentiation occurs due to a reduction in cell number in females, whereas cell number
in males remains approximately unchanged up to age of 50 years
(Hofman and Swaab, Exp Clin Endocrinol, 1991)
Dimorphism of INAH in relation to gender and sexual orientation
Individuals who died of complications of AIDS
Individuals who died of causes other than AIDS
An individual who was a bisexual man and died of AIDS
(Le Vay, Science 1991)
INAH 3 > in heterosexual men
Homosexual men INAH 3 = Women INAH 3
INAH 3 is dimorphic with sexual orientation
The sexual orientation has a biological
substrate
Comparison
SDN-POA
• volume 2.2 higher in man
than in woman
• Cell number about 2
times higher in man
INAH
• INAH1 8% > in HIV+
• INAH2 volume 2 times higher
in man
• INAH3 volume 3 times in man
• INAH4 no dimorphism
Dimorphism of INAH in relation to gender and sexual orientation
Individuals who died of complications of AIDS
Individuals who died of causes other than AIDS
An individual who was a bisexual man and died of AIDS
(Le Vay, Science 1991)
INAH 3 > in heterosexual men
Homosexual men INAH 3 = Women INAH 3
INAH 3 is dimorphic with sexual orientation
The sexual orientation has a biological
substrate
Dimorphism in relation to gender and sexual orientation
VOLUME
Suprachiasmatic nucleus
Swaab et al, Progr Brain Res, 1992
SDN-POA
Dimorphism in relation to gender and sexual orientations
Suprachiasmatic nucleus
SDN-POA
The nucleus
of the Stria
Terminalis
The nucleus of the stria terminalis (BST)
may be easily identifyed by means of
Somatostatin distribution.
men
Homosexual men
women
transsexual men
• Larger volume in men (a)
than in women (b)
• In homosexual men (c) the volume
is
similar to that of normal men
• In transsexual men with female
orientation (d) the nucleus has a
volume similar to that of women
The BST volume is reflecting the
sexual orientation rather than the
genetic sex.
The nucleus
of the Stria
Terminalis
men
women
The nucleus of the stria terminalis (BST)
may be easily identifyed by means of VIP
distribution.
• Larger volume in men (a) than in
women (b)
• In homosexual men (c) the volume
is similar to that of normal men
• In transsexual men with female
orientation (d) the nucleus has a
volume similar to that of women
Homosexual men
transsexual men
The BST volume is reflecting the
sexual orientation rather than the
genetic sex.
Man
Oxytocin neurons in
the human SON
Woman
Oxytocin neurons do not
shown any difference