It looks like you're using an Ad Blocker.
Please white-list or disable AboveTopSecret.com in your ad-blocking tool.
Some features of ATS will be disabled while you continue to use an ad-blocker.
Some gray and white matter regions of the brain are sexually dimorphic. The best MRI technique for identifying subtle differences in white matter is diffusion tensor imaging (DTI). The purpose of this paper is to investigate whether white matter patterns in female to male (FtM) transsexuals before commencing cross-sex hormone treatment are more similar to that of their biological sex or to that of their gender identity.
DTI was performed in 18 FtM transsexuals and 24 male and 19 female heterosexual controls scanned with a 3 T Trio Tim Magneton. Fractional anisotropy (FA) was performed on white matter fibers of the whole brain, which was spatially analyzed using Tract-Based Spatial Statistics.
In controls, males have significantly higher FA values than females in the medial and posterior parts of the right superior longitudinal fasciculus (SLF), the forceps minor, and the corticospinal tract. Compared to control females, FtM showed higher FA values in posterior part of the right SLF, the forceps minor and corticospinal tract. Compared to control males, FtM showed only lower FA values in the corticospinal tract.
Our results show that the white matter microstructure pattern in untreated FtM transsexuals is closer to the pattern of subjects who share their gender identity (males) than those who share their biological sex (females). Our results provide evidence for an inherent difference in the brain structure of FtM transsexuals.
One working hypothesis behind transsexuality is that the normal sex differentiation of certain hypothalamic networks is altered. We tested this hypothesis by investigating the pattern of cerebral activation in 12 nonhomosexual male-to-female transsexuals (MFTRs) when smelling 4,16-androstadien-3-one (AND) and estra-1,3,5(10),16-tetraen-3-ol (EST). These steroids are reported to activate the hypothalamic networks in a sex-differentiated way. Like in female controls the hypothalamus in MFTRs activated with AND, whereas smelling of EST engaged the amygdala and piriform cortex.
Male controls, on the other hand, activated the hypothalamus with EST. However, when restricting the volume of interest to the hypothalamus activation was detected in MFTR also with EST, and explorative conjunctional analysis revealed that MFTR shared a hypothalamic cluster with women when smelling AND, and with men when smelling EST. Because the EST effect was limited, MFTR differed significantly only from male controls, and only for EST-AIR and EST-AND.
These data suggest a pattern of activation away from the biological sex, occupying an intermediate position with predominantly female-like features. Because our MFTRs were nonhomosexual, the results are unlikely to be an effect of sexual practice. Instead, the data implicate that transsexuality may be associated with sex-atypical physiological responses in specific hypothalamic circuits, possibly as a consequence of a variant neuronal differentiation.
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 = 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.
The fetal brain develops during the intrauterine period in the male direction through a direct action of testosterone on the developing nerve cells, or in the female direction through the absence of this hormone surge. In this way, our gender identity (the conviction of belonging to the male or female gender) and sexual orientation are programmed or organized into our brain structures when we are still in the womb. However, since sexual differentiation of the genitals takes place in the first two months of pregnancy and sexual differentiation of the brain starts in the second half of pregnancy, these two processes can be influenced independently, which may result in extreme cases in trans-sexuality. This also means that in the event of ambiguous sex at birth, the degree of masculinization of the genitals may not reflect the degree of masculinization of the brain. There is no indication that social environment after birth has an effect on gender identity or sexual orientation.
Transsexuality is an individual's unshakable conviction of belonging to the opposite sex, resulting in a request for sex-reassignment surgery. We have shown previously that the bed nucleus of the stria terminalis (BSTc) is female in size and neuron number in male-to-female transsexual people. In the present study we investigated the hypothalamic uncinate nucleus, which is composed of two subnuclei, namely interstitial nucleus of the anterior hypothalamus (INAH) 3 and 4.
Post-mortem brain material was used from 42 subjects: 14 control males, 11 control females, 11 male-to-female transsexual people, 1 female-to-male transsexual subject and 5 non-transsexual subjects who were castrated because of prostate cancer. To identify and delineate the nuclei and determine their volume and shape we used three different stainings throughout the nuclei in every 15th section, i.e. thionin, neuropeptide Y and synaptophysin, using an image analysis system.
The most pronounced differences were found in the INAH3 subnucleus. Its volume in thionin sections was 1.9 times larger in control males than in females (P < 0.013) and contained 2.3 times as many cells (P < 0.002). We showed for the first time that INAH3 volume and number of neurons of male-to-female transsexual people is similar to that of control females. The female-to-male transsexual subject had an INAH3 volume and number of neurons within the male control range, even though the treatment with testosterone had been stopped three years before deat
Despite a range of research on gender identity disorder (GID), at present there is no scientific consensus on whether the etiology of GID is mental or physical. In particular recent advances in the technology of neuroimaging research have led to an increased understanding of the biological basis of various mental disorders. GID also should be evaluated from this perspective. The aim of the present study was therefore to do the first trial to examine the regional cerebral blood flow (rCBF) in GID.
Persons considered biologically male fulfilling the GID criteria are termed male to female (MTF) and, conversely, persons considered biological female are termed female to male (FTM). We compared 11 FTM subjects and nine age- and handedness-matched female control subjects. None of the subjects was regularly taking medication and none had any kind of physical or psychiatric comorbidity. To evaluate rCBF in GID subjects and control subjects, statistical parametric mapping analysis of (99m)Tc-ethyl-cysteinate dimer single-photon emission computed tomography was used.
GID subjects had a significant decrease in rCBF in the left anterior cingulate cortex (ACC) and a significant increase in the right insula compared to control subjects.
The ACC and insula are regions that have been noted as being related to human sexual behavior and consciousness. From these findings, useful insights into the biological basis of GID were suggested.
originally posted by: Morrad
a reply to: dashen
I am not actually saying anything. I have presented some scientific links. None of these links suggest this.
Sexual hormones and the brain: an essential alliance for sexual identity and sexual orientation.
originally posted by: Morrad
TransgenderTranssexual females (male to female) who have their penises removed as part of sex reassignment surgery, do not experience this phantom sensation.
originally posted by: dashen
So are you saying gender dysphoria in men can be cured with testosterone?
originally posted by: dashen
So are they saying testosterone levels in utero can affect mtf gender dysphoria later in life
The human fetal brain develops in the male direction through a direct action of testosterone and in the female direction through the absence of such an action. During the intrauterine period, gender identity (the conviction of belonging to the male or female gender), sexual orientation, cognition, aggression and other behaviors are programmed in the brain in a sexually differentiated way. Sexual differentiation of the genitals takes place in the first 2 months of pregnancy, whereas sexual differentiation of the brain starts in the second half of pregnancy. This means that in the event of an ambiguous sex at birth, the degree of masculinization of the genitals may not reflect the degree of masculinization of the brain.
Our observations on reversed sex differences in the brains of transsexual people support the idea that transsexuality is based on an opposite sexual differentiation of
(1) sexual organs during the first couple of months of pregnancy, and (2) the brain in the second half of pregnancy. There is no proof that the social environment after birth has an effect on the development of gender or sexual orientation and hormonal changes during puberty do not seem to be responsible of the adult sexual identity and orientation, while the possible effects on sexual differentiation of the brain by endocrine disrupters in the environment and in medicines given to the pregnant mother
should be investigated.
The differences observed in the INAH3 in relation to sexual orientation and gender identity and this structure’s possible connection with the BSTc suggest that these two nuclei and the two earlier described nuclei that were found to be related to gender and sexual orientation, i.e. the SDN-POA (= intermediate nucleus = INAH1 and 2) and SCN, are all part of a complex network involved in various aspects of
sexual behavior. Neurobiological research on sexual orientation and gender identity in humans is only just gathering momentum, but the evidence shows that humans have a vast array of brain differences. There is a need for further multidisciplinary research on the putative influence of testosterone in development, e.g. in individuals with complete androgen-insensitivity syndrome.
The full study can be downloaded in pdf if you do not have access to PubMed
Relationship of transsexual to transgender
Around the same time as Benjamin's book, in 1965, the term transgender was coined by John Oliven. By the 1990s, transsexual had come to be considered a subset of the umbrella term transgender. The term transgender is now more common, and many transgender people prefer the designation transgender and reject transsexual. The term transsexual, however, continues to be used, and some people who pursue medical assistance (for example, sex reassignment surgery) to change their sexual characteristics to match their gender identity prefer the designation transsexual and reject transgender. One perspective offered by transsexual people who reject a transgender label for that of transsexed is that, for people who have gone through sexual reassignment surgery, their anatomical sex has been altered, whilst their gender remains constant.
Historically, one reason some people preferred transsexual to transgender is that the medical community in the 1950s through the 1980s encouraged a distinction between the terms that would only allow the former access to medical treatment. Other self-identified transsexual people state that those who do not seek sex reassignment surgery (SRS) are fundamentally different from those who do, and that the two have different concerns, but this view is controversial, and others argue that merely having some medical procedures does not have such far-reaching consequences as to put those who have them and those who have not (e.g. because they cannot afford them) into such distinctive categories. Another reason for objecting to the term transsexual is the concern that it implies something to do with sexuality, when it is actually about gender identity. For example, Christine Jorgensen, the first widely known person to have sex reassignment surgery (in this case, male-to-female), rejected transsexual and instead identified herself in newsprint as trans-gender, on this basis.
originally posted by: Morrad
Sapolsky used the term transsexuality so I checked on Wikipedia which says transgender is more common. It also says the following so I am guessing you are in the second camp (highlighted in bold).
One perspective offered by transsexual people who reject a transgender label for that of transsexed is that, for people who have gone through sexual reassignment surgery, their anatomical sex has been altered, whilst their gender remains constant.
Other self-identified transsexual people state that those who do not seek sex reassignment surgery (SRS) are fundamentally different from those who do, and that the two have different concerns, but this view is controversial