Chemical

There’s a major debate in the field of sex determination concerning the development of brain sex. Originally it was suggested that the brain was sexed by a “hormone wash;” because males have surges of testosterone early in life, it was assumed these waves of “male” hormone were what pushed the brain into a male configuration. More recent studies, however, have discovered differing levels of expression of ~50 genes in the brain between males and females—and these genes are being expressed prior to the development of the gonads (i.e. testes and ovaries)! Other studies, examining transsexual brains (in effort to uncover aetiology of brain sex) suggested that HRT had no effect on brain morphology. This is, of course, is an encouraging finding, especially considering that the brains of MTF transsexuals were comparable to those of non-transsexual women and FTM brains were comparable to non-trans men. This suggested that our brains are naturally developed opposite our bodies—which is exactly the story we’ve been telling medical professionals for decades. Zhou et al.’s studies in which they found MTF transsexuals had a feminized bed nucleus of the stria terminalis (Nature 378.2 1995). Zhou was looking for a sexually dimorphic region of the brain that was not influenced by sexual orientation, and he came across the BST, known to play a role in mammalian sexual behaviour, it also was known to be 2.5 times larger in females than in males, and was known to house both oestrogen and androgen receptors. In his study, Zhou reported that hormones did not affect the relative size of the BST, and therefore HRT was a non-issue.
Subsequent studies, however, have suggested that the BST isn’t fully sexually dimorphic until adulthood (Chung, Vries, and Swaab, 2002). Might this mean that, indeed, Zhou et al’s studies were tainted by HRT? Still others (Blanchard) have suggested that homosexual and non-homosexual transsexuals have distinct aetiologies—this is getting into that fun area of autogynophilia vs. “true-transsexualism” that I, generally, dismiss as utter bullshit.

More recent studies, however, have told different stories. Now the issue of whether or not HRT affects brain morphology is open for debate, and researchers controlling for HRT have found that MTF transsexuals, prior to HRT, have brain morphology that is more similar to that of men. However, one specific area—the right putamen—is feminized in MTF transsexuals (Luders et al. NeuroImage 2009). What role this brain structure plays is still unknown, though it raises whole new questions. It appears that there’s a bit of a discrepancy in the scientific community. What this means, of course, is that there are some vexing questions in the field of brain sex determination (to say the least).

It’s amazing what a chemical—a little bit of estrogen or testosterone—can do. Before I transitioned and well before I knew the meaning of the word “transsexual,” I had a tremendous crush of a gorgeous red-haired girl named Lauren. I wanted nothing more than have a romantic relationship with her—hell, I may have even wanted a sexual relationship; I did, after all, have the libido of a teenage boy. I also had all the horrible awkwardness that came with having the external physical anatomy of a teenage boy along with those pounding waves of testosterone (or...rather, I had small, albeit significantly-sized waves). This meant masturbation, and lots of it (just what you all wanted to read about!). And while the crush died away (there’s a much more awesome story here...I’ll tell you sometime) the libido never did. Right up into college, I was plagued by those damn inches of manhood, peeking their way up in an effort to undermine my gender. Even HRT, while stemming the tide, did not completely arrest that thriving sex drive. At this point, I think I was sexual (i.e. I would have wanted to have sexual relationships with people as well as romantic relationships). All that changed, however, when I had my GRS. After surgery, the libido—the interest in sex and possibly romance—all had vanished.

In a recent email, Dr. Marci Bowers told me, “Post-op drops in libido are the norm rather than the exception and are an unintended consequence of GRS...Your testosterone levels are lower and probably could use a boost. I know most do not want testosterone in their blood but all women have some and it really is responsible for libido...they make an estrogen/testosterone pill called estratest or estratest HS (half strength)...you could try that or try a testosterone cream applied directly down there. It will also reduce the threshold to reach orgasm which many find difficult in achieving despite sensation.”

It makes me wonder what far-reaching effects these chemicals have. It raises the question of whether or not the orchiectomy has left me hormonally imbalanced, and whether or not this huge androgen deficit is now affecting not only my sex drive, but my sexual identity—and then what else might it be affecting? If adult hormone levels affect brain morphology, then what effects are my current hormone levels having? Is it worth it to try out testosterone treatment? Overall, I’m starting to feel comfortable in my differentness and comfortable with my sexuality...or general lack thereof. It might be worth it, down the line, to try out testosterone, but for now I suppose the most important question of all is why should I care? But I do care; all this has brought up one disconcerting issue: to what extent am I just a product of chemicals? How much of my identity is dictated in my neural chemistry—and how does that same identity change in relation to hormone levels and gene expressions? Important to all these questions is the underlying assumption that a fundamental, essential identity exists outside body chemistry, genetics, environment and socialization—that we must be more than the sum of our parts. As a scientist, I want 1+1+1+1 to equal 4; but as a human, vain and craving something more meaningful, I don’t want this to be the totality of all being.

This is what is at the heart of sex determination studies: what makes us human? Why do some of the brain sex study results differ? If trans women have an over-all masculine brain, how is it we come to self-identify as female in a culture that so harshly pushes conformation to the contrary? Are these identities—gender, sex, sexuality—firmly grounded within our cells or are they more fluid? If the later, how can scientists control for all the dynamic processes?

But maybe that’s the underlying truth? Identity—whether it is gender, sexual, social, etc.—perhaps is much more complex, multilayered, and dynamic than we assume. Regardless of what someone may tell you we are nowhere near knowing what “causes” transsexuality or cissexuality—now, just reading over the papers, the issue seems increasingly nebulous. In the face of the clusterfuck of potentially contradictory and controversial evidence, I take a step back. Matt Ridley is one of my favourite scientific authors, and at the end of his acclaimed book, Genome, he wrote the following:

A gene for free will would not be such a paradox because it would locate the source of our behavior inside us, where others cannot get it. Of course, there is no such gene, but instead there is something infinitely more uplifting and magnificent: a whole human nature, flexibly preordained in our chromosomes and idiosyncratic to each of us. Everybody has a unique and different endogenous nature. A self.

Our biology is not static, so why should we assume our social identities are? We are more dynamic—our identities more flexible. Perhaps it would be more comforting to have everything settled in a clean, Mendelian fashion—a gene for introversion here, the gay gene over on chromosome 7, and the transgender gene nestled tightly along the short arm of chromosome 16. We don’t get off that easy. The sooner we become comfortable in the natural variation and plasticity of our identities, the sooner we’ll be able to lovingly accept ourselves and each other.

References:
Zhou, J.N., Hofman, M.A., Gooren, L.J., Swaab, D.F., 1995. A sex difference in the human brain and its relation to transsexuality. Nature 378, 68–70.

Blanchard, R., 1989a. The classification and labeling of nonhomosexual gender
dysphorias. Arch. Sex Behav. 18, 315–334.

Blanchard, R., 1989b. The concept of autogynephilia and the typology of male gender
dysphoria. J. Nerv. Ment. Dis. 177, 616–623.

Chung, W. C., De Vries, G. J., & Swaab, D. F. (2002). Sexual differentiation of the bed nucleus of the stria terminalis in humans may extend into adulthood. Journal of Neuroscience, 22, 1027-1033.

Luders, E., et al., Regional gray matter variation in male-to-female transsexualism, NeuroImage (2009), doi:10.1016/
j.neuroimage.2009.03.048

Ridley, Matt. Genome. Harper Perennial. 2000