Aspies For Freedom

This may have been thought of or written about before, I have not specifically read this theory myself, or my theory may expand on what others have thought.


Raised levels of testosterone prenatally and the effects on the gender development of the embryo.

As we know it has been found that there can be raised testosterone levels in the womb when an autistic child is developing (from studies by Baron Cohen), and that as adults many of us continue to have higher testosterone levels for our gender.
I think that the higher levels of testosterone could be directly causing more males to develop, but more significantly affecting the gender in a way which affects the genital development, but not the mental development.
Therefore, if there were 10 embryos with average levels of testosterone 50% would develop into males, mentally and physically (as they would have the correct amount of testosterone for each gender).
In my theory there would be 10 embryos with raised levels (these raised levels could be from the mother, or from the embryo itself) and because of the raised levels 7 will become male on the spectrum, and 3 will become female on the spectrum. This would account for the higher numbers of males compared with females, but more importantly the mental gender of those embryos as adults would be affected.
Of the 7 males, 2 that would have been female under average circumstances would feel mentally female and have gender confusion, the 3 that were born female would have a 'male brain' and would be more likely to be lesbian or bisexual or feel as if they should have been born male. In other words, the testosterone would affect their mental gender and identity in various ways that would be unique for each individual. These factors would also be affected by childhood conditions, parental expectations, understanding of autism as they child grew up, and cultural norms for their society (such as expectations of average male and female behaviours).

I think this theory could explain the higher rates of GID and LGBT issues with autism. It certainly explains a lot for me personally, and for others I have discussed personal issues with.

I welcome opinions, my figures are just examples and not meant to be specific ratios.

Gender differentiation in the womb is not caused solely by high levels of testosterone. It is mostly genetically based, not hormonal... Since males have a Y chromosome that women do not, they have many genes that are completely absent in women that are largely responsible for them being phenotypically male.

This is why a woman with high testosterone levels who is phenotypically female and a man with low testosterone levels (the same as the aforementioned woman's levels) will still look quite different - they will still be clearly male and female, despite having equal amounts of testosterone in their bodies.

This is also why female-to-male transsexuals will never become completely physically male, no matter how much testosterone they are given. There are many physical differences between males and females that have nothing to do with testosterone.

Take Complete Androgen Insensitivity Syndrome, for example - people with this condition are genetically male (they have XY sex chromosomes), but their bodies for whatever reason are completely immune to the effects of testosterone. They will still produce the hormone, but it won't affect their bodies. When they are born, they are for all intents and purposes phenotypically female because they have not been masculinized by testosterone in the womb.

But as they get older, differences between XY women and XX women become more apparent. First of all, they have testicles, albeit undecended and nonfunctional ones. Whether the gonads in the embryo differentiate into ovaries or testes is not affected by testosterone, it is completely genetic.

Second, these women still have genes on the Y chromosomes that make their bodies produce the anti-Mullerian hormone, which prevents a female reproductive tract from forming. Their vaginas are only about two-thirds the length of normal vaginas and end abruptly - they have no cervix, uterus, or oviducts.

Third, XY women tend to be several inches taller than XX women, because there are many growth genes on the Y chromosome that women do not typically have. Contrary to what most people assume, the fact that males tend to grow taller than women is not due to increased levels of testosterone; it again is largely determined by genes.

In conclusion, I'm basically saying that testosterone levels are not what determines gender... High testosterone levels are the result of being male, not the other way around. I do think the higher fetal testosterone levels hypothesis may have some truth to it, since testosterone is known to markedly affect the way a fetus' brain works. It also fits in with the fact that most of us exhibit a "male" digit ratio, and possibly the higher LGBT ratios in autistics than in the general population (though I don't think I've noticed a higher level of gay men, at least on here).

I dunno... I guess the only way you can test a hypothesis like this is to monitor the fetal testosterone levels of thousands of unborn babies and see how many of them turn out to be autistic.

It has already been monitored, and it was found that the autistic ones had higher testosterone in utero. And it was not being male that caused it, it is not known specifically what was causing it, though autistic women who were pregnant were part of the study.

And to clarify I am not talking about a foetus, I am talking about a zygote/embryo in extremely early development before its gender has developed in any way whatsoever.

That's interesting that they have monitored the fetal testosterone levels, I did not know they had done that already and it was positively correlated with autism. Did the study find that autistic women produce higher levels of testosterone as adults as well or just inside the womb? I think I show traits of high fetal testosterone levels, but now I think they may be quite low - that is, I'm not very hairy, never had bad acne, have a curvy figure, etc.

In regards to the sex ratios, though, if you had 10 zygotes (before any gender differentiation) and 50% were XX and 50% XY, the amount of testosterone produced by them would be irrelevant. It would be impossible to get seven male fetuses (XY) and three female fetuses (XX) from a previously equal mix. Now if the amount of testosterone an adult woman produced had something to do with making it easier or harder for a zygote of a certain genetic sex to implant in the uterine lining, that would be something to test if they haven't already.

The study was by Simon Baron Cohen at Cambridge, so the results will be online somewhere.

Firstly, whether a zygote has XX or XY genes, early embryonic development is identical for both male and female - i.e. all early embryos appear female. It is the presence of the Sry gene on the Y-chromosome that turns the early, undifferentiated gonads into sperm-producing testicles for a boy instead of ovaries for a girl.
http://www.ncbi.nlm.nih.gov/books/bv.fcg...iggrp.3716



Secondly, males are missing large numbers of gene-pairs because the Y-chromosome is considerably smaller than the X. The X-chromosome doesn't just carry sex-specific information like the Y-chromosome. So if there is a defect in a gene (or it is missing) on the X-chromosome inherited from the mother, a daughter may have the correct copy inherited from the father and therefore won't have problems. However, the shorter Y-chromosome inherited from the father won't have a corresponding gene and sons will therefore have the trait; e.g. colour-blindness, hæmophilia and Duchenne muscular dystrophy.

For a girl to inherit such a condition, either both her parents must have it, or both her father and her mother's father must have it!

Medlne plus has a godd explanation of heritability and proportions.

For instance, my father is colour-blind, my mother is not.

That means that I, and both my sisters are 'carriers' of the faulty-colour-vision gene on the X-chromosome we inherited from our father, but we inherited normal vision from our mother. My brother, however is NOT colourblind and cannot be a carrier.

Back to me. Every time I conceived a child, that child had a 50/50 chance of being male or female. Each son had a fifty/fifty chance of inheriting either the healthy X-chromosome that I got from my mother, or the colour-blind one I got from my father.

As it happens, half my four sons are, indeed, colour-blind.

My husband isn't colour-blind. Our daughter therefore has a 50/50 chance of being either a carrier like me (in which case the odds for her children are the same as mine, as her other half isn't colour-blind) or perfectly 'normal'.

In America, seven percent of males are colour-blind; only 0.4% of American women are colour-blind (See here).

Because of the rarity of sex-linked disorders, the odds stack up unfairly in favour of females; females are so rarely affected that many of these disorders are assumed to be male-only. It could also be the case in many disorders that a double-dose of the faulty gene (which would have to be the case for a female to present with the disorder) is lethal to a female embryo. I have only one surviving daughter, but four sons. A friend of mine never carried a girl to term, but has three sons.

If researchers have assumed in the past that autism is a 'sex-linked disorder', they won't often be looking for ASDs in girls; and when they do, will only look for the worst cases in proportion to their theories about the ratios of sex-linked disorders.

It is very unlikely that autism actually has anything whatever to do with sex-linked inheritance; the earlier socialisation of girls is much more likely to be the reason that 'milder' cases of autism in females are missed completely and is therefore a possible sign that 'nurture' rather than 'nature' might have the biggest influence on how 'functional' someone is; not on whether they are ND or NT, but on how likely it is that they will get a diagnosis of Asperger's rather than HFA or LFA, or indeed any diagnosis at all.

But the current state of knowledge about how the 'male' brain develops is not good enough to state that it is all down to testosterone; yes, that particular hormone does have a major effect, but the embryonic brain is already 'masculinised' before testosterone production begins! There are apparently many other influences.

Unfortunately hereditry isn't that simple. (wish it were) As part of the union of male and female chromasomes mixing and sorting occurs on each chromasone. This complicates matters. I won't go into the theory about that unless someone with a biological bent would like to. I'm exhausted from university.

And in some cases (hemophilia) a positive genotype makes breeding virtually impossible, so there are no women with the disorder.

If autism is controlled by numerous genes, one or two might be sex-linked, which would explain the discrepancy.

Phenotype.  Not genotype.  Bleh.

Phenotype, of course. I do make silly errors myself. It comes with the aspies.

The testosterone theory does NOT rely on hereditary factors. It could be random anomalies, or genetic factors. Lets not forget that GENETIC does not have to mean HEREDITARY. Downs Syndrome babies are not born from Downs Syndrome parents.
Yet it is clear that Downs Syndrome is genetic.

The factors that make an embryo into a boy or girl are not as precise as you describe in practice Tigger. Some transexuals that have been genetically tested find they have XXXY chromosomes for example. Autism is making numerous difference to the brain and body, something is happening before birth that makes the changes.

<nitpicking>Actually there's a form of Down Syndrome called "partial trisomy 21" which is caused by Robertsonian translocation and is heritable. Also, Down Syndrome is usually considered a chromosomal abnormality, not a genetic one</nitpicking>

A person who has Klinefelter syndrome has some anatomical differences from a male with an XY set of chromosomes, but nothing dramatic enough to make them be considered female.

As far as I know, despite all the millions that have been poured into genetic research into autism, no-one has yet found a single obvious genetic difference between autistic and non-autistic people.

Otherwise there would likely be a definitive test already. There certainly isn't something as obvious as a chromosomal difference.

Identical twins have a higher likelihood of both being autistic than do fraternal twins; despite having the same genetic make-up and similar womb environments there isn't a 100% correlation - some figures I have read suggest 60% of identical twin pairs are both autistic. My fraternal twin sons are both autistic, but then so are both their parents.

Some studies of sibling pairs, both of whom are autistic, suggest that fraternal twin pairs are four times more likely than other pairs of siblings to be autistic; identical twins are twelve times more likely both to have autism than other sibling pairs.

So some combination of genetic pre-disposition, womb environment and 'unknown factors' is coming into play - which is why the testosterone theory doesn't completely explain what is going on, and the announcement last september doesn't claim that testosterone causes autism. Prof. Baron Cohen is looking for evidence to support his "autism=extreme male brain" hypothesis.

The most recent study I saw showed a 92% concordance for autistic spectrum conditions, and a 60% concordance for autism itself.

Here's all the twin studies to date: (http://en.wikipedia.org/wiki/Heritabilit...in_studies) - the one I'm quoting is the 1995 British study, as all later studies don't seem to look at the entire spectrum.

This still leaves the possibility of a 100% genetic "autistic spectrum" genetic pattern, as we all know that many people miss out on diagnoses solely on technicalities - and the extra 8% seems a small enough amount to cover these people...

(**edited to get rid of accidental smiley**)

In what I have read on the Twin studies, it was found that either both twins were on the same position on the spectrum (however they chose to work that out) and the others were in different positions, which at first gave the impression that one was NT. So one might have been diagnosed autistic and the other had aspie traits for example.

As far as there not being marked genetic differences (or chromosomal) I think there have been definite markers found, not enough to form a complete picture, but certainly enough for Baylor to have been working on a prenatal test.