The feedback-loops between gender identity, real life experiences, cultural concepts, genes and hormones are complex and messy, but there is a growing consensus among scientists that hormones do play a role in the creation of transgender identities.
The main focus is on the pre-natal period, when that person is still in its mother’s womb, being exposed to hormones aimed at triggering the development of gender specific organs and a gender identity.
Mapping the genes of trans women
In a paper called “Genetic Link Between Gender Dysphoria and Sex Hormone Signaling” Madeleine Foreman, Lauren Hare, Kate York, Kara Balakrishnan, Francisco J Sánchez, Fintan Harte, Jaco Erasmus, Eric Vilain and Vincent R Harley reports on a research project including 380 transgender women who have transitioned and 344 control male subjects.
They have looked at associations and interactions between variants of 12 sex hormone–signaling genes and gender dysphoria in transgender women.
These are genes that are involved in the production of hormones or the body’s ability to “read” and act on these hormones. They may be responsible for undermasculinization and/or feminization of the brain.
As far as the repetition of genes go, they do not find much of a difference between trans and cis respondents. Nor did they find any significant variation in one-letter differences between the genes of those trans and those not trans.
The main difference is found in the way genes interact. Some gene combinations seem to increase the chances of being transgender. One gene may affect the effect of another gene, which again may lead to a "feminization" of the brain.
To give one example of how one such gene may affect gender identity development:
“The minor, C allele of SULT2A1 is associated with elevated sex hormone–binding globulin, a glycoprotein that regulates circulatory sex steroid bioavailability and is present within fetal male blood during early gestation. In transgender women with the TC SNP, we speculate that fetal sex hormone–binding globulin levels are increased, which may reduce the effects of circulating hormones.”
Words of warning
There is a tendency towards oversimplifying stories like these. No doubt we will find statements like “scientists find the transgender gene!”
This is not the case. Keep the following in mind:
- They are looking at a large number of genes, which may (or may not) cause the development of gender dysphoria.
- They are looking into the interaction between genes, in the sense that you may need two or more to develop gender dysphoria.
- Researchers will also have to look at epigenetics, i.e. to what extent such genes are activated due to other causes.
- They are looking at statistical aggregates. Not all of the transgender women have one or all of these gene variations. Moreover, some of the cis men may have some of them.
- They are deliberately looking at a sample of Caucasian subjects (in order to reduce the number of variables).
In summary, the results of our study of transgender women support the hypothesis that gender dysphoria has a polygenic basis, involving interactions among multiple genes and polymorphisms that may alter the sexual differentiation of the brain in utero, contributing to the development of gender dysphoria in transgender women.backstrokerjc has translated the paper into Plain English over at reddit.
However, although discordance rates for gender dysphoria suggest that genetics plays a role, it is not the sole determinant of gender identity. Genome-wide association studies, and genome and methylome approaches, especially when coupled with neuroimaging or sex steroid measurements, should be undertaken to better understand how genetic variants contribute to gender dysphoria.
(A variant of this post was originally published over at Trans Express).
Photos: Deagreez and Tetiana Lazunova
Photos: Deagreez and Tetiana Lazunova