Brain Sex Studies and Transsexualism: What’s up with the BSTc and INAH3?

What is up with the BSTc hype?

In certain brain sex studies that have been completed, it has been found that the BSTc volume and neuron count of m2fs is about the same as it is for natal females. This was found to be true, regardless of sexual orientation, age of onset (transition), and regardless of exposure or lack of, to female hormones, in study subjects.

Likewise, the BSTc size and neuron volume of f2ms is about the same as it is for natal males.

What is the role of the BSTc in GID or transsexualism?

Currently, no one knows. This is important because, you cannot simply point to this study, and then claim “m2f transsexuals are neurologically women”. That is a huge ginormous conclusion-leap that is not substantiated by the current evidence.

What about the INAH3 hype?

Simply, INAH3 is another brain structure along with the BST that is located in the hypothalamus. Like the BST, the INAH is sexually dimorphic. This means that these structures are different sizes in males and females. While the BST does not become fully sexually dimorphic until early adulthood, the INAH differentiates between the ages of 2 to 4. Unlike the BSTc, the INAH3 is morphologically responsive to sex hormones. Meaning it will change size somewhat, due to male or female hormone exposure.

A recent study demonstrated findings much like the BST results. The physical size and neuron counts of the INAH3 in males was greater than in females. Transwomen had INAH3 values similar to women.

What is the role of the INAH3 in GID or transsexualism?

Unknown. We don’t have that information at present. This is important because, you cannot point to the INAH literature and say, “male-to-female transsexuals are neurologically female”. That is not what these findings indicate. They simply demonstrate that having a small limbic nucleus in certain areas is something that it seems m2fs share with natal females. That’s all it means.

What about the “Smell Study”?

One study was done in which a certain steroidal scent was offered to natal males and females as well as f2m and m2f transsexuals. The study showed that the brain area activated in natal females and m2fs was very similar. So you could say, male-to-female transsexuals process certain smells like born-females. Interesting findings, but that is all you can say about that study.

Sexual behavior and sexual dimorphism, what do they have to do with transsexual brain studies?

Sexual dimorphism is differences in size or features, in males and females. Some examples in nature are: Most male bears, seals, ducks, deer and the sperm whale are larger than the females. Most praying mantis, golden orb weaver, black widow spider and killer whale females are larger than the males.

Certain sections of the human brain, namely the center of the bed nucleus of the stria terminalis and the third interstitial nucleus of the anterior hypothalamus are larger in males and transmen, and comparatively smaller in females and transwomen. The BSTc is sexually dimorphic in early adulthood, while the INAH3 is sexually dimorphic in early childhood.

Changes in the size and activation of the BST in rats has demonstrated a relationship to male rat sexual behavior. For a variety of nerdy reasons, researchers have assumed that the human BST is also related to human sexual behavior.

Human sexual behavior is not playing dress-ups, or acting girly or manly. It’s not how you walk and talk and comport yourself, which would be gendered behavior, which is learned through socialization. Sexual behavior has to do with sex, actual copulation. It encompasses arousal behavior, courtship displays (flirting), and the act of sex itself.

In males, this is generally mounting behavior and ejaculation. In females, it is lordosis, and “receptive” posturing. It tends to be instinctive, as in, hardwired into your neurology. But there is an Italian study floating around out there, which demonstrated that castrated male rats given estrogen would go into lordosis when mounted by aroused and intact male rats.

What do these brain sexual dimorphism and atypical morphology findings really mean? What do they have to do with being trans?

The brain dissection studies and the Smell Study simply demonstrate that m2f transsexuals share some (as in, not all) brain morphology (structure and function) as natal-females. That’s all.

To use journalistic lingo, these studies are: “tantalizing”, “compelling” and “suggestive”. In terms of what these studies mean in relation to someone presenting with GID symptoms, or what having “female neurology” means for transsexualism, no one knows. And we are still a long way away from having fully established what female or male neurology encompasses.

That means you can drop the “Transwomen are female because they were born neurologically female, and since chromosomes and genitals can be confusing sometimes, neurology is really the only valid metric that counts for determining sex” nonsense, because that is not what these studies show. Got that transjactivists?

It is more accurate (at present) to say, “Transwomen have some shared neurological morphology with natal-females.” That’s it.

With that said, these findings help to understand, or at least shed some light on, why the trans tropes “born in the wrong body” or “always knew I was female” or “trans is a birth defect” propagate. Transsexuals are differently wired compared to people who have always felt comfortable in their sex and gender, this much is certain. How much of that different wiring occurs before birth and how much of it is developmental remains to be fully understood.

So what about the brain-imaging study?

Interestingly, a relatively recent brain imaging study indicated that pre-transition or pre cross-sex hormone exposed brains of m2fs showed brain volumes that are largely the same as non trans male brains. The study showed that in as little as four months, male brains treated with estrogen began to take on brain volume characteristics of natal-females.

What can we conclude from that brain-imaging study?

Simply, estrogen treatment feminizes the male-bodied brain, and taken from my own personal experience, these brain changes absolutely helps transwomen to think and feel more “female”.


These studies have some design flaws that need to be overcome, such as small number of brains dissected, and in some cases, lack of proper control groups for comparisons.

Also, a study that is “suggestive” or “compelling” is not the same as “conclusive” or “well-established fact”. Therefore, these studies need to be repeated and repeated again, with better controls and larger sample sizes, before any transwomen can run their mouth on the internets or IRL and claim, “transwomen are neurologically female”.

But even if it were true, so what? It takes more than a sexually dimorphic brain structure difference or two, to define “being female”. Proclaiming that these limited studies prove m2fs are “really born female”, is pure pomo bioreductionist transcentrist crap. It’s desperate fantasy.

It’s fantasy because, whether you want to admit it or not, your bodily sex sets a role for your childhood. If you have a penis, you will probably be socialized male, and you are never at risk of experiencing the unique issues of female biology, such as menses and vulnerability to unwanted impregnation.

It’s desperate because, without bioreductionist answers, you have nothing medical or biological to back you up when you try to explain to friends, family and employers (or insurers) what it means to be transsexual, which sucks.

My personal prediction is that with more studies, and similar research findings, the eventual conclusion will be: brain sex and neurology have an important role to play in biasing the transperson to what is currently being called “gender dysphoria”, and their desire to transition to the opposite sex.

How that opposite sex brain morphology asserts itself as dysphoric feelings of being in the “wrong body”, is anyone’s guess at this time. As it stands now, I think it is a fragile thing to hang your identity or validity on these measly transsexual brain sex findings.


Mostly the same PubMed articles that some transwomen spam on trans-critical feminist blogs and spaces. I did not bother to define BSTc or IANH3, (or things like the amygdala or the hypothalamus). Google helps.

Regional gray matter variation in male-to-female transsexualism
Sex dimorphism of the brain in male-to-female transsexuals
A sex difference in the hypothalamic uncinate nucleus: relationship to gender identity
A sex difference in the human brain and its relation to transsexuality.
Male-to-Female Transsexuals Have Female Neuron Numbers in a Limbic Nucleus
Male-to-female transsexuals show sex-atypical hypothalamus activation when smelling odorous steroids
Sexual Orientation: Toward Biological Understanding
Sexual differentiation of the human brain: Relation to gender identity, sexual orientation and neuropsychiatric disorders
The microstructure of white matter in male to female transsexuals before cross-sex hormonal treatment. A DTI study.
Bed nucleus of the stria terminalis: cytoarchitecture, immunohistochemistry, and projection to the parabrachial nucleus in the rat
Changing your sex changes your brain: influences of testosterone and estrogen on adult human brain structure-

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15 Responses to Brain Sex Studies and Transsexualism: What’s up with the BSTc and INAH3?

  1. Nicky says:

    The problem their is, they will still brow beat with the disproven brain study over and over as if it was still new and current. Also people like Zoe Alan Brain will still peddle it around as if it’s scientific fact.

  2. susantgolighlty says:

    One of these days research will come up with a gay gene and a trans gene, (I’m being facetious here.) And when they do, I will probably be the only gay trans person that doesn’t have the gene. So, then people will say to me that I’m not really gay or trans. I just think I am; I just need more therapy. Wait a minute, people are already telling me I need therapy because I don’t think I’m a man. Personally, I think that even if they found conclusive evidence of a correlation between brain dimorphism and being trans or gay, nothing will change. There will be those transphobic and homophobic people who will always feel that socialization will always trump physicality or vise versa. Because there are people who will want to believe what they want to believe and they don’t want to be confused by new information.

    • plasticgirl says:

      You’ve been around the scene so you would know what I am talking about when I say a trans gene would be just what we need to divide the “T” community even more. When I came out to transgender vs transsexual identity politics, I noticed it was clearly a more-feminine-than-thou trans-purity narrative competition. Back then we used to theorize that a trans gene would settle the question once and for all: who is the “true ts” (the ones with a super-special trans mutation that gives us feminine brain-feelings and lady behaviour-circuits) and who are merely committed dress-ups players and body-mod enthusiasts. With a gene test, we could have made a room of our own kind: the X-men TS mutant-elite. TS gene checks as the door – no CD-TVs allowed! So much tears that would have caused! Then finally TS could seem “true” and “authentic” and would not have to be lumped into a third-race political identity body with folks like A. Lawrence or V. Prince.

      Another thing to consider is: what structure is supported or maintained by a quest for a transsexual gene or a transsexual brain-test? Medicalization of gender-as-sex. Because we don’t have cyberpunk body shops with a la carte menu of procedures, we are required to go through the Patriarchy Pony Show and get our heads examined, so we can get a diagnosis, so we can get modded. Because no real man on earth would want his talleywhacker inverted unless he had major major mental health problems, naturally. Therefore we must be labeled as less-than men and disordered in the mind, because nothing else makes sense in the court of psychiatric opinion for why we would want surgeries. As long as being trans is seen as a medical or mental disorder, there will always be:

      a stigma attached to it
      a desire to prove one’s ts-illness bonafides
      a pre and post transition identity that manifests around being one of the specially disordered, a ts “survivor” identity. A.k.a., out and proud to be a trans woman, “I survived my gender dysphoria and now I am really really unique and special and you all must fall in love me (and, fyi! not doing so is morally very bad!)

      All pretty sad actually, imo. Not the being proud to be trans part per-se, the proud to be special because of a disorder identity or “defect of nature” that is manifest in online trans communities.

  3. susantgolighlty says:

    Sometimes I think I’m the only trans person who thinks being born trans sucks. Oh, I’ve learned to accept myself, and even be happy with myself, but I wouldn’t wish it on anybody. What I don’t understand is why does anybody want to be anything. Why don’t we just want to be humans. Of course it’s not that simple, but in a way it should be. I mean, once it dawns on us that gender, and even sex are socially constructed, why then do we continue to pursue being one or the other? Maybe it is because we all want to belong to some group and be identified with that group–even when it reifies the gender binary and an oppressive caste system based on ones genital configuration.

    Oops, I got serious again. Sometimes, I think human society is really really weird. And, if we don’t laugh, we will surely cry.

    • Tobysgirl says:

      But you are totally right that we should just want to be humans (one problem being that we have to learn how to be humans, and most of us don’t do so well at that). I don’t at all agree that sex is socially constructed, I spend too much time with animals and plants to think that, but sex carries few connotations besides reproductive ones except for the nonsense we load it with.

      Yes, unfortunately, it seems that being part of a group drives most people. I don’t particularly understand because I am marginalized and content to be marginalized, but everything I have ever observed of other humans demonstrates a powerful hunger to be part of an “in” group no matter how pathetic the group is.

      And you are also right that human society is REALLY REALLY weird! Just wait until you get older — your realization of its weirdness only increases!

    • plasticgirl says:

      And, if we don’t laugh, we will surely cry.

      You are so right! Sometimes one can lead to the other for even more delicious lability.

      I mean, once it dawns on us that gender, and even sex are socially constructed, why then do we continue to pursue being one or the other?

      I don’t know about you, but I wanted to see if I could, because I always wanted to.

  4. susantgolighlty says:

    “I don’t know about you, but I wanted to see if I could, because I always wanted to.”

    I can understand that. My thinking is that we grew up with two models of behavior–male behavior or female behavior. So yeah, if it was just a matter of choosing, I would, of course, choose female. However, why do we call certain types of behavior male behavior or female behavior? Isn’t this sexist and essentialist? I want to just look at all behavior and do (perform) the behavior that best reflects my feelings, my sensitivities, and who I am.

    In a complex social system where behaviors have political ramifications, and certain acts have political fallout. We find in certain circumstances we have to choose one or the other. So, in general, what is known as female behavior best reflects my sensitivities and my sense of self. I just don’t like thinking that certain behaviors are female or male. For instance, society in general sees reproductive work as female work–female responsibility. Personally I think that idea is totally socially constructed. Sure women give birth to children and often maternally bond to their child, but not all women give birth, and not all women who give birth bond with the offspring.

    On the other hand there are men who come alive through nurturing others, raising children, being kindergarten teachers, etc. Of course society generally thinks there must be something wrong with these men. I used to be a midwife, and I have delivered a number of babies at home births. The men (usually husbands) who helped with the childbirth usually bonded quite strongly with the new child, and were more willing (even eager) to take part in reproductive responsibilities.

    Our world is very screwed up. When we call certain types of human behavior male or female behaviors, these attitudes are learned and often taken for granted, however they are learned and not necessarily universal. We live in a world where half the population rules over and dominates the other half. In fact, life is often very dangerous for the oppressed half. No matter how you look at it, we live in a crazy fucked up world. It is a world where men are taught, programmed and conditioned to not feel, to not be able to feel connectivity with other humans. To feel entitled to have what they want even if it involves taking from others. Women, on the other hand, because they often live in a state of fear, and are raised to depend on others for survival (even their oppressors), have learned to form close bonds with one another. They have learned, like all oppressed people, to help one another, and to depend on one another for survival. Forming connections with other people is a matter of survival. These are not female behaviors, they are the learned behaviors of the oppressed.

    These are all learned behaviors. None of these behaviors are innate for one sex or the other. They are just learned behavior. Some male children are born with a desire to feel and make connections that are strong enough to override social “training.” Some women are born with a desire to have power over others, and to find security in power. It is an uphill battle for them, but nevertheless they can persist and sometimes achieve their goal.

    For me, I don’t want to have power over others. I don’t want to fill my mind, heart, and soul with hate. I cry at Hallmark Card commercials. I get sappy over puppies and babies. I cry when I’m happy. I enjoy watching romance movies.

    I don’t know where I’m going with this, but I’m not choosing to be a woman or to be female, I’m choosing the type of life I want to live. I can only think of three things that can be sex linked. These are menstruation, childbirth, and nursing. There is nothing that men can do that women can’t do. So, besides from these three things, all behaviors are just human behaviors–the good ones with the bad ones. So, I choose the good ones. Choosing the good ones has nothing to do with gender or gender presentation.

    Sorry to be so wordy. Jefferies book has really got me thinking.

    • plasticgirl says:

      There is nothing to apologize for, Susan. I don’t mind wordy.

      With lovely comments like yours, comments that just take me aback for a moment and make me think, “Wow. Your mind is amazingly similar to mine in some ways,” you are more than welcome to take up as much space as you’d like.

    • plasticgirl says:

      We live in a world where half the population rules over and dominates the other half. In fact, life is often very dangerous for the oppressed half. No matter how you look at it, we live in a crazy fucked up world. It is a world where men are taught, programmed and conditioned to not feel, to not be able to feel connectivity with other humans. To feel entitled to have what they want even if it involves taking from others. Women, on the other hand, because they often live in a state of fear, and are raised to depend on others for survival (even their oppressors), have learned to form close bonds with one another.

      This is something I worried intensely about pretransition, because I did not have bonding experiences with people after about six or seven years old. I had to learn to deliberately socialize in order to fit in.

      When Lisa Vogel says she wants a space free of “male energy”, I don’t think most transwomen understand what that means. But if there is a male energy, there is a counterpart and that is female energy and one of those “girl-energy” type things I wanted to understand, is why for example, do women go to the restroom together?

      When I started hanging out with women, I just followed the leader and emulated, as it were. But later after some bad run-ins with men, and the knowledge that guys are sometimes in the restroom (or follow you to the restroom, over even hover around one acting poorly like they aren’t hovering, in order to get your attention), that it might be nice to have support from someone who knows about how you are vulnerable and can provide the safety-in-numbers needed to offset a lone or small group of predators. Plus it gives you a chance to talk about gossip about certain male individuals in the group with some privacy.

      Another way I tried to deal with being socialized to take, was to learn to give, and giving and receiving in sharing is a bonding experience.

  5. Tobysgirl says:

    The behaviors you detail, Susan, are of course socially constructed behaviors. My mother was an anthropologist and there are societies in which men do the child-rearing; in these societies child-rearing is the status occupation! It is also easy to forget that in agricultural communities, men tend to spend far more time with children than urban or suburban men do. When a man came to fix our washing machine, he brought his young daughter with him and they talked the whole time he was working.

    I don’t believe we are born to much of anything, though some of us may have higher natural levels of oxytocin. In a more human needs-centered world, all of us would be increasing our natural levels through nurturing one another, children, animals, plants, the planet (petting a dog raises the human’s level AND the dog’s level). But we live in a world that values aggression and cruelty and devalues community and warmth (and it is not taking us to a good and healthy place).

    Interestingly, as an androgynous woman, I don’t particularly like all-female environments. I just cancelled a salon appointment because I cannot stand sitting there waiting for the hair color to take and being forced to listen to gossip (so loud you can’t shut it out no matter how hard you’re trying to read your New Yorker). I like intelligent people wherever I meet them, which is extremely infrequently, and I prefer people who have something to talk about other than who’s divorcing whom. I’m beginning to realize why my grandmother and mother became so isolated; one has little tolerance as one ages for people who have no cultural or intellectual life, no political consciousness, and really nothing to say.

    And, yes, these are super discussions!

    • plasticgirl says:

      I don’t believe we are born to much of anything, though some of us may have higher natural levels of oxytocin. In a more human needs-centered world, all of us would be increasing our natural levels through nurturing one another, children, animals, plants, the planet (petting a dog raises the human’s level AND the dog’s level).

      I agree Tobysgirl. Also, that sounded like a request! Which also reminds me, in my old body, I was always kind of like “meh” about small children and animals (maybe just how testo worked on my brain). But after the first year or two of estrogen, I began to see baby’s faces in animals. I think it’s called anthropomorphizing? I think my next post will be more about my pregnancy dreams.

      Just gaze at this clean piglet and let it calm you

      Oh, and speaking of dreams, another post I am going to do is a new narrative on becoming a transwoman. Part of that narrative is that I used to have transformation dreams; dreams of becoming a woman.

      Pretty much after I started taking estrogen, I never had a mtf transformation dream again.

  6. Heya! I’m att work browsing ʏourr blog from my new iρhone 4!
    Just wanted to say I love reading through your blog аnd look forwɑrd to all your posts!
    Carery on the fantastic work!

  7. plasticgirl says:

    incidentally trannies, tyfanz, warpathianz, spack, and all self appointed gender therapists and armchair early transition theorists…


    can smell pheromones on men and women. and. while i was a procumslut, a bblagp client double blind tested me with scent vials. i detected testo correctly first time.

    progesterone shots give me phantom cramps

    i get fibrosymptoms but usually yoga keeps them away

    i have anorexia and i weigh almost one hundred pounds less than last year at the same time due to all the mtt stalking my social mediazz

    my hands and feet are icy at all times unless ive just fed or had an orgasm

    my voice can vibrate plate glasd storefront windows

    by screwing up my post srs care routine, i got my pussy to smell like a honey pot

    i am multiorgasmic. i was pre ànd post srs

    i have almost no adams apple, naturally

    i love my small firm natural breasts.

    the smell of my thighs and feet compels men to try to fuck me.

    ive had pregnancy dreams since childhood

    i identify as female

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