The biology behind Caitlyn Jenner

According to a study done by the University of Vienna, there are substantial differences in the microstructures of brain connections between transgender and cisgender people, or people whose gender identity agrees with their assigned sex at birth. 

 

 

“Everyone should know this stuff” Level

Unless you have been living under a rock, names like Chaz Bono, Laverne Cox, and Caitlyn Jenner should definitely ring a bell. From differences such as being an on-television beautician stuck in the slammer in Orange is the New Black to having parents like Sonny and Cher, there is one thing that they all have in common—they are all transgender. By definition, being transgender means that your binary gender identity, or the fixed “feminine” and “masculine” identification,  is the opposite of your anatomical sex. In other words, a transgender man is considered a biological female who identifies as a man and a transgender woman is a biological male who identifies as a woman.

Although the definition of “transgender” is pretty clear, being transgender is anything but simple. The Diagnostic and Statistical Manual of Mental Disorders once deemed transgenderism as “Gender Identity Disorder” and only after years of lobbying did that term get removed and replaced with “Gender Dysphoria” (Beredijick 2012).  Dysphoria is a state of uneasiness or dissatisfaction. The issue gender advocates had with labeling something as a “disorder” is that it suggests that all transgender people are mentally ill and should, in effect, be seeking psychiatric attention—something they should not be doing unless they feel “dysphoric,” or extremely distressed (Beredijick 2012).

The nature versus nurture debate has always accompanied the idea of gender identity and for many decades experts believed that the environment led to gender dysphoria (Beredijick 2012). Many believed that gender identity, like boy/girl gender roles, is a social construct. Therefore, gender identity is determined simply by how a child is raised (Beredijick 2012). For this reason people in the transgender community have been sidelined and abused because their gender identity has been viewed simply as psychological issue or worse—a “choice” (Beredijick 2012).

However, neuroscientists around the world have found that gender identity is in fact nature (biologically determined) and not nurture (environmentally determined) (Hampson 2015). According to a study done by the University of Vienna, there are substantial differences in the microstructures of brain connections between transgender and cisgender people, (people whose gender identity agrees with their assigned sex at birth) (Hampson 2015).

Neurobiologist, Dr. Dick Swaab, proposes that testosterone is essential in influencing gender identity (Hampson 2015). There are two surges of testosterone that happen during the gestation period of pregnancy. In the first half of gestation the rush or lack of testosterone impacts the development of genitals (Hampson 2015). In the second half of gestation, the rush or lack of testosterone shape the brain in terms of setting gender identity to the male or female extreme (Hampson 2015).

The perception of one’s gender identity is connected to sexual differentiation in the brain (Saraswat 2016). Scientists have found that there is an apparent difference in the phenotype, observable traits,  of transgender people (Saraswat 2016). Transgender-specific cerebral phenotypes have even been  reinforced by postmortem brain studies (Saraswat 2016).

“For geniuses only” Level

In the same way that there is mounting evidence for transgenderism being biologically determined, there is mounting evidence against it. Skeptics argue that the main way to investigate innate and biological human characteristics is through twin studies. If in fact something is genetically determined and one twin expresses a trait, so should the other (Whitehead 2000). In other words, if transsexuality is genetic, and one twin identifies as transgender, so, too, should the other (Whitehead 2000).

However, of the four sets of identical male twins studied in which one twin identified as transgender, there was only one case in which both twins were transgender (Whitehead 2000). Whitehead argued that since the brain shapes differently with response to behavior, the argument that the microstructures we are born with are unalterable (Whitehead 2000). There is scientific evidence that brain microstructures change with experience (Whitehead 2000). Therefore, it’s more valid to argue that the brain differences between transgender and cisgender people are a result of transsexual experience rather than actual being born with a brain microstructure abnormality (Whitehead 2000). According to Whitehead, the studies done showing hormonal abnormalities, brain microstructure differences, and psychological states are poorly replicable and only show minor links to transgenderism (Whitehead 2000). However, even though there are minor links we cannot simply chalk up the differences found in brain structure between transgender and cisgender people to coincidence.

Impress your friends and family with these three related facts:

Fact 1: Transgender females were found to have longer repetitions of the androgen receptor, a nuclear receptor that is activated by the binding of testosterone and is vital in the development of primary and secondary male sex characteristics (Wikipedia 2016). This genetic abnormality, consequently, reduces the capability of binding testosterone (Wikipedia 2016).

Fact 2: A variant genotype, CYP17, acts upon sex hormones pregnenolone and progesterone and the loss of this gene variant are linked to transgender males (Wikipedia 2016). Transgender males commonly have this gene variant as well as an allele distribution similar to male controls and different from female controls (Wikipedia 2016).

Fact 3: 24 transgender females who have not yet undergone hormone treatment were studied via MRI, although their grey matter concentrations were more similar to male than female, there was a vastly larger volume of grey matter in the right putamen compared to the average man (Wikipedia 2016).

Author: This article was written by Laissa Duclos, a senior at Choate Rosemary Hall in Wallingford, CT. Laissa’s spirit animal is a monkey. Someday, Laissa will be famous for setting the world record for saying “literally” more than Kim Kardashain.

Works Cited

Beredjick, C. (2012).DSM-V To Rename Gender Identity Disorder ‘Gender Dysphoria.’Advocate. 23 July 2012. (Date Accessed 12 February 2016) http://www.advocate.com/politics/transgender/2012/07/23/dsm-replaces-gender-identity-disorder-gender-dysphoria

Hampson, S. (2015). Science in Transition: Understanding the Biologybehind Gender Identity. The Globe and Mail. 19 July 2015. (Date Accessed 2 February 2016)http://www.theglobeandmail.com/life/science-in-transition-understanding-the-biology-behind-gender-identity/article25553156/

Saraswat, Aruna. (2015).  Evidence Support the Biological Nature of Gender Identity. Medscape. (Date Accessed 5 February 2016) http://www.medscape.com/viewarticle/840538_3

Whitehead, NE. (2000). Is transsexuality biologically determined? MyGenes.co. (Date accessed 1 February 2016).http://mygenes.co.nz/transsexuality.htm

Wikipedia. (2016). Causes of transsexualism. Wikipedia. (Date accessed: 4 February 2016) https://en.wikipedia.org/wiki/Causes_of_transsexualism#Biological-based_theoriesis