Male-to-Female Transsexuals Show Sex-Atypical Hypothalamus Activation When Smelling Odorous Steroids

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.

[Dyssonance]

nyah nyah

[Dyssonance]

well, yet more evidence of a neurological form of IS.

[Dannie F]

Layman's terms please. Anyone?

[Dyssonance]

Male to female transsexuals are born with women's brain's, not men's.

[Pauline]

Dyssonance wrote:

Male to female transsexuals are born with women's brain's, not men's.

And a whole lot more.Some have female organs that were sewed up or cut off. hormone problems, AIS-CAH and a hundred more. Almost all know from the time they learn the difference between a boy and a girl. but we are not allowed to live like we feel. I envy the hell out of the kids of today. 4-5 and treated like a girl, or a boy if the other way.
am1-2

[Pauline]

Transpeople can tell when using a mens room when forced to It stinks to high heaven. Testosterone just reeks. been 10 years and I hope it last forever. Men stand and piss on a wall and splatter everywhere.

I can imagion if they went into the ladies room and the mess the wall would be. PU.

[Will]

1. Have any studies confirmed the implicit assumption in this "working hypothesis" that these sex-atypical brain networks were present from birth?

2. Since transexuals receive hormone treatments which also could produce alterations in certain hypothalamic networks, how does this "working hypothesis" control for this possible confounding factor?

[Dyssonance]

yes, and read the study (it isn't that hard to figure out)

[Zoe Brain]

Dyssonance wrote:

Male to female transsexuals are born with women's brain's, not men's.

That's an over-simplification.
The only areas we [b]definitely[/b] know are cross-gendered are in the lymbic nucleus, a very basic and primal part of the brain, which is connected with emotions, sexual orientation, body map, gender identity, and sense of smell. The latter is completely absent in some Intersex conditions (e.g. Kallmans syndrome) which should have been a dead giveaway.
Other parts of the brain may also be affected. And that's not counting cases of medically-induced transsexuality due to neonatal surgical cross-gendered assignment of Intersexed children.
In short: it may be an over-simplification, but close enough. The bit of the brain that determines gender identity is cross-gendered in transsexuals.

[Zoe Brain]

And of course lesbian MtoFs are described as "nonhomosexual".*SIG H*

[Will]

Zoe Brain wrote:

<quoted text>
That's an over-simplification.
The only areas we [b]definitely[/b] know are cross-gendered are in the lymbic nucleus, a very basic and primal part of the brain, which is connected with emotions, sexual orientation, body map, gender identity, and sense of smell. The latter is completely absent in some Intersex conditions (e.g. Kallmans syndrome) which should have been a dead giveaway.
Other parts of the brain may also be affected. And that's not counting cases of medically-induced transsexuality due to neonatal surgical cross-gendered assignment of Intersexed children.
In short: it may be an over-simplification, but close enough. The bit of the brain that determines gender identity is cross-gendered in transsexuals.

WRONG -- that "bit of the brain" does NOT "determine[] gender identity", if by "determine" you mean "cause".

"Correlation" is not necessarily "causation", and even as you pointed out, there's NOT even a perfect "correlation" here! The correlation may be "close enough" for YOU but it is NOT close enough to establish causation to a high degree of scientific certainty.

The fact is certainly not lost on you that all of these "hypothalamic activity" studies focus on highly selective "regions of interest" in the brain, to the exclusion of perhaps relevant activity in other areas of the brain -- a fact that you must have taken notice of because you observed the caveat that: "Other parts of the brain may also be affected."

[Dyssonance]

Hey, Zoe!!!

What the hell is a rocket scientist doing here?

(giggle)

Welcome to Topix, Zoe -- last bastion of anonymous, cowardly, and craven bashing of the whole darn LGBT crowd.

Will -- the one that misrepresents anything they touch -- is one of the few that's actually got half a brain and uses it.

(and now you'll figure out where my less than pleasant verbal habits have come from, lol)

[Dyssonance]

Zoe Brain wrote:

<quoted text>
That's an over-simplification.
The only areas we [b]definitely[/b] know are cross-gendered are in the lymbic nucleus, a very basic and primal part of the brain, which is connected with emotions, sexual orientation, body map, gender identity, and sense of smell. The latter is completely absent in some Intersex conditions (e.g. Kallmans syndrome) which should have been a dead giveaway.
Other parts of the brain may also be affected. And that's not counting cases of medically-induced transsexuality due to neonatal surgical cross-gendered assignment of Intersexed children.
In short: it may be an over-simplification, but close enough. The bit of the brain that determines gender identity is cross-gendered in transsexuals.

Agreed, it certainly is oversimplified.

What I found personally interesting about this article is that it provides yet a little more indication that there are surprising variances -- but, a with some of the other studies done of late, we are having to wait for the duplications.

The recent imaging stuff has been fascinating, but, as I think you'll agree, there's a certain degree of risk involved in its development of a screening tool, at least in terms of the political issues.

[Dyssonance]

Will wrote:

<quoted text>
WRONG -- that "bit of the brain" does NOT "determine[] gender identity", if by "determine" you mean "cause".
"Correlation" is not necessarily "causation", and even as you pointed out, there's NOT even a perfect "correlation" here! The correlation may be "close enough" for YOU but it is NOT close enough to establish causation to a high degree of scientific certainty.
The fact is certainly not lost on you that all of these "hypothalamic activity" studies focus on highly selective "regions of interest" in the brain, to the exclusion of perhaps relevant activity in other areas of the brain -- a fact that you must have taken notice of because you observed the caveat that: "Other parts of the brain may also be affected."

Given you haven't a point of reference for what she's talking about, Will, you might want to retract the above statement.

Oh, and Will? Meet ZoeB. She's a friend of mine.

[Will]

Dyssonance wrote:

<quoted text>
Given you haven't a point of reference for what she's talking about, Will, you might want to retract the above statement.
Oh, and Will? Meet ZoeB. She's a friend of mine.

LOL, I won't hold that against her.

And my "points of reference" are this article, the 'hypothamalic response to pheromones' studies of Ivanka Savic et al., and ZoeB's own comment.

[Pauline]

Will wrote:

1. Have any studies confirmed the implicit assumption in this "working hypothesis" that these sex-atypical brain networks were present from birth?
2. Since transexuals receive hormone treatments which also could produce alterations in certain hypothalamic networks, how does this "working hypothesis" control for this possible confounding factor?

Only problem is that many Transpeople can not medically take the cross hormones, they react to their detrament, and they still end up the same way.

[Dyssonance]

Will wrote:

<quoted text>
LOL, I won't hold that against her.
And my "points of reference" are this article, the 'hypothamalic response to pheromones' studies of Ivanka Savic et al., and ZoeB's own comment.

Good. You can still do something smart on occasion :D

Those Points aren't enough to be able to draw the conclusions you have, given that you don't know what her comment was referring to in full, only in part.

Which is why you were so far off base.

[Zoe Brain]

You really have to look at the article in full - not just the abstract - and in context.
I've quoted some of it on my blog, at http://aebrain.blogspot.com/2008/07/more-part... . I've included one of the more useful parts, the list of references.
Taken together with the other papers mentioned at http://aebrain.blogspot.com/2008/06/bigender-... , a more complete picture emerges.
To go back to basics, when you have a correlation between phenomena A and B, there are 4 possible causal relationships. A could cause B, B could cause A, both A and B could be caused by another phenomenon, C, or it all could be coincidence.
At this stage, while each of the papers individually cannot exclude coincidence, in toto it beggars belief, given absence of any contrary evidence, that there is no causal relationship. In practical terms, there are many medical treatments universally accepted as "proven" based on less certain evidence.
So, we have A - transsexuality - and B - a plethora of cross-gendered or partially cross-gendered morphology in the lymbic nucleus - an possibly elsewhere.
So could A cause B? There is no hypothesis that would explain such a thing. Hormones and neurotransmitters can be ruled out, and they are the only mechanism (other than gross physical trauma) we know of where neural morphology can be changed by environment (see PTSD etc). On the other hand, behavioural signs of transsexuality appear long before such morphological changes are visible.
Could B cause A? The timing is wrong, as I said above. Transsexuals have behavioural differences long before observed sexual neural differentiation of some structures, which occur at puberty. On the other hand, the same kinds of gender-differentiatated behaviours occur before observable sexual differentiation of neurology in cisgendered people too. There's something sexually differentiated in neurology that happens early, and is associated with behaviour controlled by the lymbic nucleus, that we can't observe yet. PET scans show some promise that we may do soon though.
Could C cause both A and B? This hypothesis is consistent with the facts. The fact that 1 in 5 DES-exposed 46xy infants are TS is inexplicable otherwise. We even have a chain of causation, based on other evidence involving hormones and mixed-gendered twins in both human and animal studies. There has to be a way, not yet well understood, in which observable pubertal development is "foreordained" by the hormonal environment in the womb. Transsexuality can be explained by more subtle effects in the same neural area before puberty - see Milton Diamond's paper on the subject, quoted at http://aebrain.blogspot.com/2008/06/bigender-... .
It is likely that genetic predisposition plays a role. The "1 in 5" TS following DES is similar to the "1 in 10" incidence of phocomelia caused by Thalidomide, the symptoms of which required genetic predisposition in the foetus.

[Zoe Brain]

I'll quote Justice Chisholm of the Australian Family Court on the subject, after a review of the evidence in 2003:
At paragraph [252]:‘The traditional analysis that they are "psychologically" transsexual does not explain how this state came about. For example, there seems to be no suggestion in the evidence that their psychological state can be explained by reference to circumstances of their upbringing. In that sense, the brain sex theory does not seem to be competing with other explanations, but rather is providing a possible explanation of what is otherwise inexplicable’.
At paragraph [253]:‘In other words (as I understand it) the brain of an individual may in some sense be male, for example, though the rest of the person’s body is female’.
At paragraph [265]:‘In my view the argument in favour of the “brain sex" view is also based on evidence about the development and experience of transsexuals and others with atypical sex-related characteristics. There is a vast literature on this, some of which is in evidence, and I can do no more than mention briefly some of the main points’.
At paragraph [270]:‘But I am satisfied that the evidence now is inconsistent with the distinction formerly drawn between biological factors, meaning genitals, chromosomes and gonads, and merely "psychological factors", and on this basis distinguishing between cases of inter-sex (incongruities among biological factors) and transsexualism (incongruities between biology and psychology)’.
At paragraph [272]:‘In my view the evidence demonstrates (at least on the balance of probabilities) that the characteristics of transsexuals are as much “biological” as those of people thought of as inter-sex’.
Proven beyond all reasonable doubt? Not quite. Not yet. Though there is no other competing hypothesis that has any evidence backing it up. Proven on the balance of probabilities? Oh yes, an strongly so.
This should really have been a blog post, not a comment, shouldn't it?

[Zoe Brain]

Part I

You really have to look at the article in full - not just the abstract - and in context.

I've quoted some of it on my blog, at http://aebrain.blogspot.com/2008/07/more-part... . I've included one of the more useful parts, the list of references.

Taken together with the other papers mentioned at http://aebrain.blogspot.com/2008/06/bigender-... , a more complete picture emerges.
To go back to basics, when you have a correlation between phenomena A and B, there are 4 possible causal relationships. A could cause B, B could cause A, both A and B could be caused by another phenomenon, C, or it all could be coincidence.

At this stage, while each of the papers individually cannot exclude coincidence, in toto it beggars belief, given absence of any contrary evidence, that there is no causal relationship. In practical terms, there are many medical treatments universally accepted as "proven" based on less certain evidence.

So, we have A - transsexuality - and B - a plethora of cross-gendered or partially cross-gendered morphology in the lymbic nucleus - an possibly elsewhere.

So could A cause B? There is no hypothesis that would explain such a thing. Hormones and neurotransmitters can be ruled out, and they are the only mechanism (other than gross physical trauma) we know of where neural morphology can be changed by environment (see PTSD etc). On the other hand, behavioural signs of transsexuality appear long before such morphological changes are visible.

Could B cause A? The timing is wrong, as I said above. Transsexuals have behavioural differences long before observed sexual neural differentiation of some structures, which occur at puberty. On the other hand, the same kinds of gender-differentiatated behaviours occur before observable sexual differentiation of neurology in cisgendered people too. There's something sexually differentiated in neurology that happens early, and is associated with behaviour controlled by the lymbic nucleus, that we can't observe yet. PET scans show some promise that we may do soon though.