Objective: To review current literature that supports a biologic basis of gender identity.
Methods: A traditional literature review.
Results: Evidence that there is a biologic basis for gender identity primarily involves (1) data on gender identity in patients with disorders of sex development (DSDs, also known as differences of sex development) along with (2) neuroanatomical differences associated with gender identity.
Conclusions: Although the mechanisms remain to be determined, there is strong support in the literature for a biologic basis of gender identity.