Recently, Dr. Keith Ablow of the Fox News Medical A-Team dismissed any biological origins of gender dysphoria, stating:
I don't believe we have definitive data (although many psychiatrists with very impressive credentials, who seem to mean well, assert that we do) that any male or female soul has ever in the history of the world been born into the wrong anatomic gender.
Let me put that more clearly: I am not convinced by any science I can find that people with definitively male DNA and definitively male anatomy can actually be locked in a cruel joke of nature because they are actually female.
One might ask, "So what sort of evidence is there that being transgender has some sort of biological origin, that indeed someone can be wired to be one gender, and physically another?"
Short answer: Lots. Here are 15 studies showing a biological origin of gender dysphoria.
1. "There is also evidence, albeit clinical, for a role of testosterone in the sexual differentiation of the human brain, in particular in inducing male gender role behavior and heterosexual orientation." - Julie Baker, Focus on Sexuality Research, 2014
2. "...We conclude that there is sufficient evidence that EDCs modify behavioral sexual dimorphism in children, presumably by interacting with the hypothalamic-pituitary-gonadal (HPG) axis." Winneke et al, Environmental health perspectives, 2013
3. "Gender-dependent differentiation of the brain has been detected at every level of organization--morphological, neurochemical, and functional--and has been shown to be primarily controlled by sex differences in gonadal steroid hormone levels during perinatal development." Chung and Wilson, European Journal of Physiology, 2013
4. "Gender identity (the conviction of belonging to the male or female gender), sexual orientation (hetero-, homo-, or bisexuality), pedophilia, and the risks for neuropsychiatric disorders are programmed into our brain during early development. There is no proof that postnatal social environment has any crucial effect on gender identity or sexual orientation." Swaab and Bao, Neuroscience in the 21st century, 2013
5. "Testosterone, estrogen and dihydrotestosterone are the main steroid hormones responsible for the organization and sexual differentiation of brain structures during early development." Serkan Karaismailoğlu; Ayşen Erdem, Journal of the Turkish-German Gynecological Association, 2013
6. "In human males, we show that variation in fetal testosterone (FT) predicts later local gray matter volume of specific brain regions in a direction that is congruent with sexual dimorphism observed in a large independent sample of age-matched males and females from the NIH Pediatric MRI Data Repository." Lombardo, et al., The Journal of Neuroscience, 2012
7. "Testosterone measured in infancy predicts subsequent sex-typed behavior in boys and in girls." Lamminmäki, et al., Hormones and Behavior, 2012
8. "The finger length ratio between the second and fourth digits in transgender men was significantly lower than in female controls in the right hand in this study. 2D : 4D showed a positive correlation with GIS score. Because 2D : 4D influences are assumed to be established in early life and to reflect testosterone exposure, our results suggest a relationship between GID-FtM and perinatal testosterone." Sasaki, Tsukamotoa, and Horie, The Journal of Sexual Medicine, 2012
9. "...growing evidence shows that testosterone exposure contributes similarly to the development of other human behaviors that show sex differences, including sexual orientation, core gender identity, and some, though not all, sex-related cognitive and personality characteristics." Hines, Annual review of neuroscience, 2011
10. "There is strong evidence that high concentrations of androgens lead to more male-typical behavior and that this also influences gender identity. "Jürgensen, et al., Journal of Pediatric Endocrinology and Metabolism, 2010
11. "However, when the process of genital development and of brain sexual development does not match the same sex, females with a male brain and vice versa can arise. These transsexual people have problems with their gender identity and have the conviction of being born in the wrong body." Worrell, Master Thesis, Faculty of Medicine, Universiteit Utrecht, 2010
12. "In this study, more than 150 individuals with confirmed or suspected prenatal diethylstilbestrol (DES) exposure reported moderate to severe feelings of gender dysphoria across the lifespan." Kerlin, Paper prepared for the International Behavioral Development Symposium, 2005
13. "Secondly, as predicted twin girls where one displayed gender dysphoria had a more masculine pattern of cerebral lateralization, than non-transgender girls. These findings support the notion of an influence of prenatal T on early brain organization in girls." Cohen-Bendahan; Buitelaar; van Goozen; and Cohen-Kettenis, Psychoneuroendocrinology, 2004
14. "It thus appears conceivable that due to local hormone dependent changes during development at least some areas of the brain may follow a different course than the genitals during the process of sexual differentiation. A partial or even complete brain-body sex reversal may eventually be the result." Kruijver, Dissertation, Faculty of Medicine, University of Amsterdam, 2004
15. "Results support the notion that the gender identity is related to the sex steroid-driven sexual differentiation of the brain, and that certain genetic variants of three of the genes critically involved in this process, may enhance the susceptibility for transsexualism." Landén, Doctoral Thesis, University of Gothenburg, 1999
The 15 studies listed above is a very small, partial list. V.S. Ramachandran has published a number of studies showing transgender individuals are wired to physically experience bodies of the opposite sex as well.
I'm not sure what would convince Dr. Ablow. It's very unlikely that we will develop a "soul-o-meter" that measures the gender of a person's inner essence. However, the body of evidence showing biological origins of gender dysphoria, of having a mis-matched brain and body, is overwhelming. Given his ability to ignore the evidence, perhaps Dr. Ablow should probably look at a board position with the Flat Earth Society membership. Or climate change denial. Either way, it gets him away from practicing psychiatry, a job for which he is obviously unqualified.
(A much larger list of studies can be found here.)