Sunday, 27 September 2009

The Effects of Hormones on the Brain

Two for the reference library:

Changing your sex changes your brain: influences of testosterone and estrogen on adult human brain structure by Pol et al, Europ Jnl Endocrinology, Vol 155, suppl_1, S107-S114 2006

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.

The findings suggest that, throughout life, gonadal hormones remain essential for maintaining aspects of sex-specific differences in the human brain.
In other words, sex hormones cause gross changes in volume in some brain structures.


Neuroimaging Differences in Spatial Cognition between Men and Male-to-Female Transsexuals Before and During Hormone Therapy by Scoening et al J Sex Med. 2009 Sep 14.

Introduction. Neuropsychological abnormalities in transsexual patients have been reported in comparison with subjects without gender identity disorder (GID), suggesting differences in underlying neurobiological processes. However, these results have not consistently been confirmed. Furthermore, studies on cognitive effects of cross-sex hormone therapy also yield heterogeneous results.

Aim. We hypothesized that untreated transsexual patients differ from men without GID in activation pattern associated with a mental rotation task and that these differences may further increase after commencing of hormonal treatment.

Method. The present study investigated 11 male-to-female transsexual (MFTS) patients prior to cross-sex hormone therapy and 11 MFTS patients during hormone therapy in comparison with healthy men without GID. Using functional magnetic resonance imaging at 3-Tesla, a mental rotation paradigm with proven sexual dimorphism was applied to all subjects. Data were analyzed with SPM5.

Main Outcome Measures. Patterns of brain activation associated with a mental rotation task. Results. The classical mental rotation network was activated in all three groups, but significant differences within this network were observed. Men without GID exhibited significantly greater activation of the left parietal cortex (BA 40), a key region for mental rotation processes. Both transsexual groups revealed stronger activation of temporo-occipital regions in comparison with men without GID.

Conclusions. Our results confirmed previously reported deviances of brain activation patterns in transsexual men from men without GID and also corroborated these findings in a group of transsexual patients receiving cross-sex hormone therapy. The present study indicates that there are a priori differences between men and transsexual patients caused by different neurobiological processes or task-solving strategies and that these differences remain stable over the course of hormonal treatment.
Some things change, some things don't. The brain's plasticity is limited, and trans women don't have the neuroanatomy men do, regardless of whether they are on Hormone Replacement Therapy or not.

And another thing that doesn't change: the labelling of trans women as "transsexual men" even when reporting clear evidence that they're no such thing. *SIGH*


Caisa said...

The second one I find very interesting. Something I've always felt but it's nice to have it confirmed.

And, yes, it's amazing that they never learn to use the right labels. It's the same here in Sweden.

Anonymous said...

Im always happy to hear about about more and more research being done. I can tolerate the labels if they are providing valuable results.

I find these results to be personally vindicating personally. Im very glad more and more seems to be coming into the light.


Nicole Joy said...

Thank you for posting these links, Zoe. I've spent a little time looking around for data on pre- and post-treatment characteristics of TS brains.

This is the sort of investigation I'd hoped to see.

Nicole Joy

riki said...

1 The first (Pol) article has been relied upon by Anne Lawrence to attack Swaab's work on the BSTc
But the Pol article is not very reliable when you read it closely (Peggy Cohen-Kettenis, one of the authors agreed with that when i interviewed her)
2 I'd like to see the actual data on the 2nd one, as the sample size is small and it is likely that the significant differnce in averages is accompanied by a wide within group variation - so that ther is lots of overlap between pre and post MTF and cis men.
3 Zoe - you have not commented on the recent Ujike article "Association study of gender identity disorder and sex hormone-related genes" (in press Progress in Neuro-Psychopharmacology & Biological Psychiatry xxx (2009) xxx–xxx)- abstract below - which directly contradicts the Hare and Henningsson studies based on a larger sample. It finds no connection with genetic variations in five sex hormone genes. Unlike the Hare article, which was feted as finding a transsexual gene,this has received no mention in any press that I can see.
The lesson? Be careful of the very common human tendencies in evaluating scientific evidence to underrate negative results and to view more positively results that you agree with.

To investigate the biological mechanism of gender identity disorder (GID), five candidate sex hormone-related genes, encoding androgen receptor (AR), estrogen receptors alpha (ERalpha) and beta (ERbeta), aromatase (CYP19), and progesterone receptor (PGR) were analyzed by a case-control association study. Subjects were 242 transsexuals (74 male-to-female patients (MTF) and 168 female-to-male patients (FTM)), and 275 healthy age- and geographical origin-matched controls (106 males and 169 females). The distributions of CAG repeat numbers in exon 1 of AR, TA repeat numbers in the promoter region of ERalpha, CA repeat numbers in intron 5 of ERbeta, TTTA repeat numbers in intron 4 of CYP19, and six polymorphisms (rs2008112, rs508653, V660L, H770H, rs572698 and PROGINS) of PGR were analyzed. No significant difference in allelic or genotypic distribution of any gene examined was found between MTFs and control males or between FTMs and control females. The present findings do not provide any evidence that genetic variants of sex hormone-related genes confer individual susceptibility to MTF or FTM transsexualism.

Zoe Brain said...

I'd be interested in the ER-beta results, as they are the only ones that the Hare paper describes.

Looks like the predictions I made in this post though have been falsified.

Of interest is this post too.

Zoe Brain said...

The Hare article found correlations in CAG for AR, but no correlation in CYP19 or ERbeta.
I don't know if it was exon 1 of AR though.

Zoe Brain said...

Exon 1 is the one usually examined, as that's the one that appears to have lots of correlations with prostate cancer, etc.

Exons 2-8 were not examined in this study, but may have been in the Hare one.

In which case, we may have narrowed things down a bit. I need to read the fine details.

Julie said...

How much faith do you have in fMRI scans? I'm still slightly suspicious that the willingness to equate fMRI indications of "brain activity" with the characteristics of thought (conscious or subconscious) represents a new kind of phrenology. We're so far from understanding the mechanics of the brain that I remain dubious about a lot of these studies. Not that I don't *want" to believe them, but the uncritical acceptance of fMRI scans as indicators of brain function worries me.

Some of my concerns may have been sparked by this article, which is completely unrelated to matters of gender:

Edward said...
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Dynevor Shannon said...

The comment about unreliability of scan information and our general knowledge of the brain, rings true. I suspect their are biological reasons for transgrenderism, just as there is (obvious from nature study of wild animals) for homosexuality. Whether gay or transgendered can yet be "found" in the brain is unknown. Some bisexual or lesbian MTF s are known to become more attracted to men when they start HRT, so sexual attraction most probably is partly hormonal. I suspect that much more minuate and unknown biological markers do exist for transgendered but we are long way from finding it. Both my brother and I are mtf (wannabes) and our half sibling is gay (likes rugby players lol). "Queenie" uncles and cousins abound!
But like homosexual versus transvestism, there is probably plenty of overlap with psychological and nurture factors. Each person is probably different to which degree of importance various factors influence their tranagenderism, but somewhere biology probably pays a part.