Transgender Identity: Let's Look at the Science

(Photo: REUTERS/Susana Vera)Contestants prepare to rehearse to compete in the "Miss World Spain" pageant in Estepona, southern Spain, October 25, 2015. Angela Ponce, the first openly transsexual woman to compete to represent Spain at the Miss World pageant, was eliminated in the first knockout round.

Editor's Note: This is Part 1 in a Christian Post series on how Christians should respond to transgenderism. 

The percentage of American adults who identify as transgender has doubled over the past decade to about 1.4 million people. And that number is expected to increase, especially as more children are now beginning to identify as someone of the opposite gender.

The Christian Post is launching this series on transgenderism as children as young as 3 are being increasingly told that it's normal to change their gender identity and as parents and institutions are being forced to accommodate and embrace transgender children.

The first part of the series will offer an overview of the science and the few studies that were done to better understand why people identify as transgender.

To begin with, let's define some terms.

Sex is assigned at birth. It "refers to one's biological status as either male or female, and is associated primarily with physical attributes such as chromosomes, hormone prevalence, and external and internal anatomy."

Gender "refers to the socially constructed roles, behaviors, activities, and attributes that a given society considers appropriate for boys and men or girls and women. These influence the ways that people act, interact, and feel about themselves. While aspects of biological sex are similar across different cultures, aspects of gender may differ."

Transgender is "an umbrella term for persons whose gender identity, gender expression or behavior does not conform to that typically associated with the sex to which they were assigned at birth."

Gender identity "refers to a person's internal sense of being male, female or something else."

Gender dysphoria (also known as gender identity disorder): "formal diagnosis given by mental health professionals to people who experience distress because of a significant incongruence between the gender with which they personally identify and the gender with which they were born."

The Science

Currently, little is known about what causes some people to reject their biological sex and identify with the opposite gender.

Previous research findings — much of it on the brain — have led some to conclude that being transgender is not a choice. But not all researchers are on board with that conclusion.

So is there a biological basis for being transgender?

Here's a look at some of the studies often cited by those who argue that transgender persons are born that way.

In 1995, a study by the Graduate School Neurosciences Amsterdam and the Netherlands Institute for Brain Research showed "a female brain structure in genetically male transsexuals."

Researchers had looked at a part of the brain called the bed nucleus of the stria terminalis (BSTc) — a brain area that is essential for sexual behavior and is larger in men than in women. They found that male-to-female transsexuals had a female-sized BSTc.

The researchers also noted that "the size of the BSTc was not influenced by sex hormones in adulthood and was independent of sexual orientation."

In a follow-up study in 2000, the same research institutions looked at the neurons — specialized cells that transmit information — in the BSTc. More specifically, they examined the number of somatostatin-expressing neurons. They found that men had almost twice as many somatostatin neurons as women.

Male-to-female transsexuals had a similar number of neurons in the BSTc to that of women. The number of neurons in a female-to-male transsexual was similar to that of men.

Researchers concluded that there could be a "neurobiological basis of gender identity disorder."

In 2009, the UCLA School of Medicine's Department of Neurology analyzed MRI data of 24 male-to-female (MTF) transsexuals not yet treated with cross-sex hormones. Researchers found that "regional gray matter variation in MTF transsexuals is more similar to the pattern found in men than in women. However, MTF transsexuals show a significantly larger volume of regional gray matter in the right putamen compared to men."

This finding, UCLA researchers said, "supports the assumption that brain anatomy plays a role in gender identity."

An additional study that has led some to make similar conclusions that being transgender is caused by genetics is a 2013 one on twins by the Pacific Center for Sex and Society in Hawaii.

Researchers use the twin study design to determine whether a trait is due to genes. Identical twins share nearly 100 percent of their genes and are raised in the same family environments whereas fraternal twins share around half their genes. Thus, "if a trait is more common among identical twins than fraternal twins, it suggests genetic factors are partly responsible." 

The Pacific Center researchers analyzed over 100 sets of twins where at least one had transitioned from one gender to the other. They found a 28.38 percent concordance among identical twins compared to a 0.34 percent concordance among fraternal twins — meaning the identical twins are more likely to both be transgender than fraternal twins are.

The results from all of these studies have been presented by many as evidence that there is a genetic basis for transgender identity.

Nevertheless, research on transgenderism is still in its infancy and there have been no "irrefutable conclusions," Reuters recently reported.

Currently, the "largest-ever study of its kind" is underway with scientists from five research institutions — including Vanderbilt University Medical Center, George Washington University and Boston Children's Hospital — exploring whether there is a genetic factor behind the existence of transgender persons.

In the meantime, findings from the aforementioned studies have been rejected by some as inconclusive or even accepted as evidence that there is no genetic cause.

Michelle Cretella, a board certified pediatrician with an interest in adolescent mental and sexual health who is also the president of the American College of Pediatricians, a conservative organization, told The Christian Post that the twin study from 2013 shows that transgender identity is not something one is born with.

"If transgenderism were 'hard wired by factors before birth,' then every identical twin would have the same gender identity, but they do not. Transgenderism is in the mind, not in the body," Cretella said. "This is why there is no medical test that can diagnose a person as transgender; we must simply take the individual's word for it because only the individual knows what he or she is thinking and feeling."

As for the research on brain structure, scholars at Johns Hopkins University in Maryland released a report in 2016, arguing that there is not enough definitive scientific evidence available to suggest that gay, lesbian and transgender individuals are born that way.

Lawrence S. Mayer and Paul R. McHugh argued that the studies had small sample sizes and need further scientific consideration.

"The question is not simply whether there are differences between the brains of transgender individuals and people identifying with the gender corresponding to their biological sex, but whether gender identity is a fixed, innate, and biological trait, even when it does not correspond to biological sex, or whether environmental or psychological causes contribute to the development of a sense of gender identity in such cases," they contended. "Neurological differences in transgender adults might be the consequence of biological factors such as genes or prenatal hormone exposure, or of psychological and environmental factors such as childhood abuse, or they could result from some combination of the two.

"There are no serial, longitudinal, or prospective studies looking at the brains of cross-gender identifying children who develop to later identify as transgender adults. Lack of this research severely limits our ability to understand causal relationships between brain morphology, or functional activity, and the later development of gender identity different from biological sex."

Hormone Therapy

A 2014 study by the American Foundation for Suicide Prevention and the Williams Institute — UCLA School of Law's think tank — showed that more than 4 in 10 trans men and trans women tried to commit suicide. The prevalence of suicide attempts was highest among those who are younger (18 to 24).