Brain Power…

“…I would while away the hours, confir’in with the flowers…. if I only had a brain…”  — Scarecrow, in the Wizard of Oz musical film.

After years of trying to explain the differences between the two types and the statistical evidence for the two type taxonomy of MTF transwomen, I’m now posting what should be the final clincher; solid biomedical laboratory evidence, “proof” even.

Decades ago, as I was researching our collective history and science (the two often go hand in hand), I came across a reference to studies that showed that gay men had feminized brains while MTF transsexuals did not.  SAY WHAT!?!?

Turns out, the study referenced made the false assumption that all MTF transsexuals are the same and had only included gynephilic older transitioners.  Other studies, being aware of, and accounting for the differences between the two MTF transsexual types found something quite interesting, as for example, from the Dörner (1983) abstract:

“In male rats, androgen deficiency during a critical period of sexual brain differentiation was shown to give rise to a predominantly female-differentiated brain. Such animals displayed “homosexual behaviour”, i.e., they were sexually attracted preferentially to partners of the same sex. In addition, they exhibited a sex-specific evocability of a positive oestrogen feedback effect. A positive oestrogen feedback effect on LH secretion was also induced in homosexual transsexual men, in contrast to hetero- or bisexual transsexual men. Thus in homosexual transsexual men, an intravenous injection of 20 mg Presomen (Premarin) produced a significant decrease of serum LH levels followed by a significant increase above the initial LH values. In hetero- or bisexual transsexual men, by contrast, intravenous oestrogen administration, while producing a significant decrease of serum LH levels, was not followed by an increase above the initial LH values. A positive oestrogen feedback effect on LH secretion was also found in homosexual non-transsexual men, in contrast to heterosexual men. These findings suggest that transsexual as well as non-transsexual homosexual men possess a predominantly female-differentiated brain which may be based, at least in part, on androgen deficiency during sexual differentiation of the central nervous system. Homosexual transsexual men also showed an increased LH and FSH response to LH-RH as compared to hetero- or bisexual transsexual men.”

Note that non-exclusively-androphilic (“heterosexual or bisexual”) transwomen did NOT have the female like positive estrogen feedback effect on LH serum levels.  Of course, according the Blanchard’s work, all “non-homosexual” MTF transsexuals should also be in the same taxon, so we would predict that so-called, asexual transsexuals should also show the lack of this positive feedback, and indeed, this too was found, as discribed in the Dörner’s (1976) earlier paper,

“In transsexual men with homosexual behaviour and intact testicular function, as well as in homosexual men with normal gender identity, following a negative oestrogen feedback effect a delayed positive oestrogen feedback action on LH secretion was evoked. By contrast, in transsexual men with hypo- or asexuality and intact testes or hypergonadotrophic hypo- or agonadism, as well as in heterosexual men with normal gender identity, a negative oestrogen feedback effect was not followed by a positive feedback action on LH release. In transsexual women with homosexual behaviour and oligo- and/or hypomenorrhoea, only a weak or at best moderate positive oestrogen feedback action on LH release was evocable, similarly as in castrated and oestrogen-primed heterosexual men. By contrast, in a transsexual woman with bisexual behaviour and eumenorrhoea, a strong positive oestrogen feedback action on LH secretion was evocable, as well as in heterosexual women with normal gender identity.”

Note that in this paper we see a mirror like difference between FtM “homosexual transsexuals” (gynephilic transmen) who respond more like heterosexual men and bisexual FtM transmen who respond more like heterosexual women.  Thus, this data would lend support for there being a taxonic difference between exclusively gynephilic and non-exclusively gynephilic transmen, mirroring the taxonic difference between the two types of transwomen.

Conclusion:

These papers, detailing a specific, repeatable, laboratory based test that can differentiate the two types of transsexuals described by Blanchard, “Homosexual” and “Non-Homosexual”, offers both supporting evidence for the two type taxonomy but potentially also a way of independently sorting the two types in future studies.  This difference is a classic medical biomarker for the two types.  Should anyone one doubt the weight of statistical evidence, we can also point to the biomedical evidence via laboratory tests.

Addendum 9/2/2017:

In exploring science, it is important not to cherry pick or ignore papers which fail to support a given hypothesis.  So, I am adding another paper to the list of reference and discussing a paper that on the surface would seem to be contradict Dörner’s results.  Unfortunately, these papers are behind paywalls and I don’t have copies of them… so I clearly don’t have the details… only the abstracts.  Gooren reported in two papers attempts to replicate the LH response and found mixed results, from the ’86 abstract,

“The neuroendocrine response of LH to estrogen administration may be related to sexual dimorphism of the brain, and therefore, homosexual and especially transsexual individuals may differ from heterosexual individuals in their responses. This study failed to find such differences among groups of female heterosexuals, homosexuals, and transsexuals. Specifically, after single dose estrogen administration, all subjects had an initial decline in serum LH levels, followed by a brisk rise of equal magnitude. Among males, the type of response was less uniform. After an initial fall in serum LH levels, the individual responses varied. In 12 of 23 male homosexuals, 10 of 15 male heterosexuals, and all 6 genetic male transsexuals studied, serum LH levels remained below pretreatment levels. In the remaining 11 male homosexuals and 5 of the heterosexuals, serum LH levels increased to values exceeding those before treatment, resembling the response found in the 3 groups of women. Those homosexual and heterosexual men with a rise in serum LH levels to above pretreatment values also had the greatest fall in testosterone levels after estrogen administration, while these same men had the lowest testosterone response to hCG stimulation. I conclude from these results that 1) the similarity of LH responses to estrogen administration in all groups of women studied does not support a theory of brain androgenization as a factor in the establishment of gender identity of sexual orientation; and 2) individual differences in men in the type of LH response to estrogen administration can be satisfactorily explained by endocrine factors, such as Leydig cell function, and need not be related to gender identity, sexual orientation, or other possible causes.”

And in an early ’84 paper,

“In order to test the hypothesis whether there is variation in hormonal levels or response to hormonal manipulation that could permit a distinction between heterosexuals and transsexuals, we designed the following protocol: Six male-to-female (m-to-f) transsexuals, six heterosexual control females and six female-to-male (f-to-m) transsexuals were given estradiol benzoate (E2B) (4.5 micrograms/kg/12 hr) for five days. In the female population, E2B treatment was initiated on day 5 of the menstrual cycle. In all the subjects blood luteinizing hormone (LH) and follicle stimulating hormone (FSH), estradiol-17 beta (E2) and testosterone (T) levels were measured twice daily. Additionally, LH and FSH responses to LHRH (100 micrograms iv) stimulation prior to and on day 5 of the E2B treatment were evaluated. In the m-to-f transsexuals, T levels decreased sharply and progressively during estrogen treatment, along with a fall in LH and FSH levels. The magnitude of the LH and FSH responses to LHRH stimulation also decreased following estrogen administration. In the heterosexual female controls and in the f-to-m transsexuals, estrogen administration increased LH levels to a minimum of 100% above initial values from day 3 onwards.  There was no convincing evidence for the existence of a positive estrogen feedback on LH secretion in m-to-f transsexuals. These results contradict some of the reported hypotheses concerning hormonal alterations in these individuals.”

However, in both studies, Gooren made no effort to differentiate between exclusively androphilic (homosexual) transsexuals and gynephilic/bisexual MTF transsexuals as Dörner did.  Given the copious evidence from statistical and brain morphology research that differentiates the two types of transwomen, this limits the utility of Gooren’s studies.  The only true dissonance between the studies is that Gooren found only a slight difference between homosexual and heterosexual (non-trans) men: 52% of homosexual and 33% of heterosexual men showing a positive LH feedback, while all 6 of the MTF transwomen failed to show any such positive LH feedback.

Although it would appear that this fails to replicate Dörner, I’m astounded that all six of the transwomen failed to show any LH feedback when at least some of the non-transfolk, both homosexual and heterosexual did so.  Without knowing which type of transsexual these subjects are, we can’t really say that this fails to replicate Dörner.  They could all be gynephilic.  There does seem to be small effect size between gay and straight men, but the sample sizes are all too small.  Further, I would be very curious as to how Dörner and especially Gooren determined the sexual orientation of their subjects and whether they were exclusively heterosexual and homosexual.

Interesting that all of the FTM transmen showed an exaggerated LH feedback, hmmmm…

Given the Gooren data, small sample as it is, perhaps adding to it another study regarding the difference between heterosexual and homosexual men?  We have such a study in Gladue, from the abstract,

“A neuroendocrine component, the positive estrogen feedback effect, thought to be related to sexual orientation and, indirectly, to sexual differentiation, was evaluated in healthy, noninstitutionalized research volunteers. Men and women with a lifelong heterosexual orientation and men with a lifelong homosexual orientation were administered an estrogen preparation known to enhance the concentration of luteinizing hormone in women but not in men. The secretory pattern of luteinizing hormone in the homosexuals in response to estrogen was intermediate between that of the heterosexual men and that of the women. Furthermore, testosterone was depressed for a significantly longer period in the homosexual men than in the heterosexual men. These findings suggest that biological markers for sexual orientation may exist.”

Although, to be fair, this study was also small, but when we add them all together, the direction of the effect seems to be real.

References:

Dörner G, Rohde W, Schott G, Schnabl C., “On the LH response to oestrogen and LH-RH in transsexual men.” Experimental Clinical Endrocrinology (1983)
http://www.ncbi.nlm.nih.gov/pubmed/6317420

Dörner G., “Neuroendocrine response to estrogen and brain differentiation in heterosexuals, homosexuals, and transsexuals.” Archives of Sexual Behavior (1988)
http://www.ncbi.nlm.nih.gov/pubmed/3282489?dopt=Abstract

Dörner G, Rohde W, Seidel K, Haas W, Schott GS.”On the evocability of a positive oestrogen feedback action on LH secretion in transsexual men and women.” Endokrinology (1976)
http://www.ncbi.nlm.nih.gov/pubmed/1244197

Gooren L. et al., “Estrogen positive feedback on LH secretion in transsexuality.” Psychoneuroendocrinology (1984)
https://www.ncbi.nlm.nih.gov/pubmed/6436856

Gooren L., “The neuroendocrine response of luteinizing hormone to estrogen administration in heterosexual, homosexual, and transsexual subjects.” Journal of Clinical Endocrinology and Metabolism (1986)
https://www.ncbi.nlm.nih.gov/pubmed/3016021

Gladue A., Green R. Hellman R., “Neuroendocrine response to estrogen and sexual orientation” Science (1984)
https://www.researchgate.net/publication/17097653_Neuroendocrine_response_to_estrogen_and_sexual_orientation

 

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