Transgender persons and transsexuals.
2017: Why are
some people transgender?
Research findings, based on imaging
studies or autopsies of brains:
Part 4 of nine parts.
An unidentified transgender woman.
Why are some people transgender? That is, why do they identify their current gender as being different from their gender that was recorded by a physician shortly after they were born on their birth certificate?
Most transgender adults had their bodies examined at birth, declared to be male, and registered as male on their birth certificate. Later in life, often as early as three years of age, they start to proclaim that their gender identity is female. They are referred to as "MTF" (male-to-female) transgender persons. They often describe themselves as having a female brain trapped in a male body. That is, somehow, their brain is telling them that even though they may possess male sexual organs, have male (probably XY) sex chromosomes in their DNA, have a male body shape, etc. their brain is telling them that they are female.
FTM (male to female) transgender persons are fewer in number; they were registered as female at birth, and develop a male gender identity later in life.
A smaller number of transgender individuals identify as both male and female, or neither male nor female.
Although many religious conservatives maintain that transgender persons are simply "gender confused," past experience has shown that this may not be accurate because no amount of counseling, therapy, or prayer has been found to be effective at "curing" them.
Studies showed that identical twins, whose DNA is the same, are more likely than fraternal twins, whose DNA are different, to both be "trans." This pointed to the probability that there might be a genetic cause to being transgender. That is, they were "set up" to be transgender before birth.
It made sense for researchers to compare the structure of brains in:
MTF transgender persons, looking for similarities with brains from cisgender females, and in
FTM transgender persons, looking for similarlities with brains from cisgender males.
The term "cisgender" refers to the vast majority of adults whose gender identity is in harmony with their body and their DNA.
Many transgender individuals explain that they have a female brain in a man's body -- or vice versa. Brain studies, whether by imaging living people or autopsies after their death, might reveal that they are accurate in their belief.
Francine Russo, writing for Scientific American reported on three studies comparing brain structures and brain reactions between transgender and cisgender persons. 2 Researchers attempted to determine if their transgender subjects' brains' structures and responses are more similar to their birth-identified gender, or to their current gender identity. Some results:
Antonio Guillamon, a psychobiologist at the National Distance Education University in Madrid and Carme Junqué Plaja. a neuropsychologist at the University of Barcelona led a Spanish team who studied the brains of 24 FTM and 18 MTF transgender persons. They used a Magnetic Resonance Imaging (MRI) instrument. They examined their subjects' brain structures both before taking hormone medication and after. Their results were published in 2013. They found that:
The FTM subjects who identified as male had relatively thin subcortical areas similar to cisgender male brains.
The MTF subjects who identified as female had thinner cortical regions in the brain's right hemisphere which is typical of cisgender female brains.
Sarah M. Burke, a psychologist at VU University Medical Center in Amsterdam and Julie Bakker, a biologist at the Netherlands Institute for Neuroscience used a functional MRI to examine the brains of 41 adolescent transgender boys and girls, testing the reaction of their brain's hypothalamus' to androstadienone. This is a substance with pheromone-like properties to which cisgender men and women respond differently. They published their results in 2014 after finding that:
The FTM adolescents who identify as male have brains that responded similarly to cisgender male brains.
The MTF adolescents who identify as female have brains that responded similarly to cisgender female brains.
- The results were less clear with 39 prepubertal children who were tested separately.
Baudewijntje Kreukels, a specialist in gender dysphoria at VU University Medical Center, said that this type of study is important:
Robert M. Sapolsky, writing for The Wall Street Journal during late 2013, said that scientists found differences in:
"... an obscure brain region called the forceps minor [that] is part of the corpus callosum, a mass of fibers that connect the brain's two hemispheres. On average, the forceps minor in cisgender males contains parallel nerve fibers of higher density than in cisgender females." 2 The researchers found that
The FTM transgender adolescents, who identified as male, had brains had a higher density nerve fibers, corresponding to cisgender males.
- The hypothalamus was also studied. It is a part of the brain that produces hormones.
The FTM transgender adults, who identified as males, had brains that are stimulated by the scent of estrogen similarly to cisgender males.
The MTF transgender adults, who identified as females, had brains are stimulated by the scent of androgen similarly to cisgender females. 3
A review article on why some people hold transgender beliefs:
A literature study was conducted by researchers at the Boston University School of Medicine (BUSM) into biologic nature of gender identity.
Corresponding author Joshua D. Safer wrote:
"This paper represents the first comprehensive review of the scientific evidence that gender identity is a biological phenomenon," explains corresponding author Joshua D. Safer, MD, FACP. "As such it provides one of the most convincing arguments to date for all medical providers to gain the transgender medicine skills necessary to provide good care for these individuals, 4
The findings of all of these studies point to:
The brains of MTF transgender persons who currently identify as female respond similarly, and are structured similarly, to the brains of cisgender females.That is, their biological sex is male, their gender identity is female, and their brain has internal female structures and responses.
The brains of FTM transgender persons who currently identify as male respond similarly, and are structured similarly, to the brains of cisgender males. That is, their biological sex is female, their gender identity is male, and their brain has internal male structures and responses.
This implies that their sense of personal gender is caused by a difference in brain structure or response, not by being in a state of "gender confusion" as conservatives frequently cite.
We have been unable to find any studies which found that the brains of transgender persons are structured similarly or responded similarly to the brains of cisgender persons who had the same birth-identified gender.