INTRODUCTION AND TERMINOLOGY
Terminology and Definitions
Gender identity is an individual’s innate sense of being male, female, both, or neither. Gender expression refers to one’s gender presentation to the world, which may or may not correlate with an individual’s gender identity or sex recorded at birth (the latter is usually based on external genitalia or sex chromosomes).
Trans, transgender, gender incongruent, and gender nonbinary are all adjectives that refer to individuals who have gender identities that differ from the sex recorded at birth. Cisgender describes individuals with gender identities that align with the sex recorded at birth. Gender identity and gender expression are not binary, but rather appear on a spectrum.1 It is estimated that transgender people in the United States make up between 0.5% and 0.6% of the population.2
Gender dysphoria is a mental health diagnosis where gender incongruence is associated with clinically significant discomfort.3 It is important to be cognizant that not every gender-incongruent individual experiences gender dysphoria.
Gender identity should not be confused with sexual orientation. Sexual orientation describes an individual’s pattern of physical, romantic, emotional and/or spiritual attraction and arousal.
Gender Identity Includes a Durable, Biological Component
Gender identity may be discordant with one’s anatomy, chromosomal sex, or sex recorded at birth. The literature consistently supports gender identity being a durable phenomenon with a substantial biological component.4 The strongest evidence of gender identity being durable comes from studies that looked at 46,XY children with congenital anomalies who were raised as girls. The most-referenced study consisted of 14 genetically male (46,XY) children with cloacal exstrophy who were assigned the female gender at birth. Eight of the 14 subjects assigned female identified as male when the report was published. In addition, 2 children were raised as males and continued to identify as males.5 A larger survey looked at the experience of 72 46,XY children assigned female at birth due to penile agenesis, cloacal exstrophy, and penile ablation. Investigators found 15 of the 72 children identified as male and 10 of the children who continued to identify as female reported significant gender dysphoria. Additionally, all but one of the children assigned to male at birth in the study continued to identify as male.6
There are several other lines of support for biology underlying gender identity. One area is the association of brain anatomy with gender identity. One postmortem study of 6 transgender women on hormone therapy found that the size of the bed nucleus of the stria terminalis (BST) in the hypothalamus in these transgender women was within the female range. Examination of a trans feminine individual who did not undergo hormonal treatment also showed BST size within the female range, and examination of a transgender man revealed a BST within the male range. No association was found between BST and sexual orientation ...