Horm Behav. 2006 Nov;50(4):589-601. Epub 2006 Jul 25.
The biology of human psychosexual differentiation.

* Gooren L.

Department of Endocrinology, Vrije Universiteit medical center, PO Box 7057, 1007 MB Amsterdam, The Netherlands. ljgooren@asianet.co.th

Most attempts to identify biological underpinnings of gender identity and sexual orientation in humans have investigated effects of sex steroids, so pivotal in the differentiation of the genitalia, showing strong parallels between animals and the human. The information on humans is derived from the so-called ‘experiments of nature’, clinical entities with a lesser-than-normal androgen exposure in XY subjects and a higher than normal androgen exposure in XX subjects. Prenatal androgenization appears to predispose to a male gender identity development, but apparently not decisively since 40-50% of 46,XY intersexed children with a history of prenatal androgen exposure do not develop a male gender identity. Obviously, male-to-female transsexuals, with a normal androgen exposure prenatally (there is no serious evidence to the contrary) develop a female gender identity, through unknown biological mechanisms apparently overriding the effects of prenatal androgens. The latest studies in 46, XX subjects exposed to prenatal androgens show that prenatal androgenization of 46,XX fetuses leads to marked masculinization of later gender-related behavior but does not lead to gender confusion/dysphoria. The example of female-to-male transsexuals, without evidence of prenatal androgen exposure, indicates that a male gender identity can develop without a significant androgen stimulus. So we are far away from any comprehensive understanding of hormonal imprinting on gender identity formation. Brain studies in homosexuals have not held up in replication studies or are in need of replication in transsexuals. Genetic studies and the fraternal birth order hypothesis provide indications of familial clustering of homosexuality but in many homosexuals these genetic patterns cannot be identified. The biological explanations advanced for the birth order hypothesis lack any experimental support.

PMID: 16870186 [PubMed - indexed for MEDLINE]

There are also a very few cases where apparently TS people have spontaneously changed apparent gender. Most of these cases are from the IS condition 5ARD, FtoM at puberty, but there’s a handful where the cause is ideopathic, MtoF at andropause. At least 3 different mechanisms have been identified, but the phenomenon is not well understood.

Finally there’s the study showing a rate of Gender Dysphoria amongst 46xy individuals exposed to the drug DES in the womb of 1 in 5.

As for me – I had Gender Affirmation Surgery 6 weeks ago. I have 46xy chromosomes, but you can’t call it a Sex Change as that would require normal male genitalia. But even the surgeon was surprised to find I had a female pattern pubic bone.

I knew I was a girl since about age 7 – pretty typical for TS women. But when you have the body of a thickset rugby player, there doesn’t seem much point complaining. Had I not been one of the women whose bodies change from M to F spontaneously (though incompletely, alas) in their 40’s, I’d still be doing the male act.

Brain structures are far more plastic then what people give credit for. People recovering from strokes and so on show that the brain can rewire itself.

Perhaps the combination of hormones and resocialization can create physiological changes in people’s brains.

Also, the sample listed below consisted of younger people. The question is what kind of changes would one see in older people.

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Eur J Endocrinol. 2006 Nov;155 Suppl 1:S107-14.

Changing your sex changes your brain: influences of testosterone and estrogen on adult human brain structure.

Hulshoff Pol HE, Cohen-Kettenis PT, Van Haren NE, Peper JS, Brans RG, Cahn W, Schnack HG, Gooren LJ, Kahn RS.

Department of Psychiatry, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, A01.126, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands.

OBJECTIVE: Sex hormones are not only involved in the formation of reproductive organs, but also induce sexually-dimorphic brain development and organization. Cross-sex hormone administration to transsexuals provides a unique possibility to study the effects of sex steroids on brain morphology in young adulthood. METHODS: Magnetic resonance brain images were made prior to, and during, cross-sex hormone treatment to study the influence of anti-androgen + estrogen treatment on brain morphology in eight young adult male-to-female transsexual human subjects and of androgen treatment in six female-to-male transsexuals. RESULTS: Compared with controls, anti-androgen + estrogen treatment decreased brain volumes of male-to-female subjects towards female proportions, while androgen treatment in female-to-male subjects increased total brain and hypothalamus volumes towards male proportions. CONCLUSIONS: The findings suggest that, throughout life, gonadal hormones remain essential for maintaining aspects of sex-specific differences in the human brain.

PMID: 17074982 [PubMed - in process]

This is not theory, but hard cold fact.

I would much prefer to have the boundaries for acceptable gender expression be expanded to include the full degree of gender expression. I would much prefer to fight for equal protection under law regardless of gender expression.

Can we please move on to a place of protection and equality under the law and from the gender theories developed by privileged mostly white academic individuals?

Poor children whose gender expression hold them up for ridicule and threaten their safety are best protected by strong defense of gender variant behavior.

History has taught us that dress does not indicate gender, And I for sure will fight for the right of an individual to control his/her own body: the right to dress in a manner appropriate for their performing work, without restrictions to gene based dress codes.

Judith Butler identifies as a lesbian. Period. A butch one at that! That is what she said when she spoke at NYU recently.

On an other note: why in the world would any parent encourage their child to hate their birth body. The real question for me comes to what in the culture causes a child to feel so different that he/she feels the only solution is to deny their birth sex and seek to be the opposite of their essence.

Les celebrate difference, lets protect gender variance as fundamental to a healthy sex identify…

People who focus too much on what made them as they are use time that could better be spent in becoming all that they are capable of.

Nerissa

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