Christine Jorgensen was an ex-GI and one of the first Americans to undergo surgical gender reassignment.

New York Daily News Archive/Getty Images

In 1952 a 27-year-old, former WWII-era GI from New York named George Jorgensen traveled to Denmark, and returned to the U.S. as Christine Jorgensen. Jorgensen, who had described herself as a woman trapped in a man's body, was one of the first to transition from the male to female gender through a process involving hormone therapy and surgical procedures [source: Hadjimatheou]. In time, she became a trailblazer in seeking those gender reassignment surgeries as these procedures, now known as gender realignment (reconstruction, affirmation or confirmation) surgeries, wouldn't begin in the U.S. until 1966 [source: Wexler].

Gender identity struggles usually begin in early childhood but descriptions of feeling like a man trapped inside a woman's body, or vice versa, have been identified in and reported by people of all ages. A person living with this an internal conflict may develop anxiety and depression, and go on to be diagnosed with gender dysphoria, formally known as gender identity disorder (GID). Gender dysphoria is a mental health condition that can arise when a person lives with ongoing feelings of being physically incongruous with his or her birth sex — and medical intervention may be beneficial. Identifying as transgender, itself, is considered by scientists to be, at least in part, biological and not a mental illness [source: HRF].

Being transgender also isn't about anatomy or sexual orientation; it's about internally identifying with a gender status — which could be masculine, feminine, agender or gender fluid — that is different than the one culturally assigned to you based upon your physical characteristics. While some people may never publicly acknowledge their transgender status, others may decide to live as their desired gender — and that could mean changing how they express their gender through transitioning.

Transitioning is often two-fold: a social transition, such as new clothing, a new name and new pronouns; and a medical transition, with treatments such as hormone therapy and surgical procedures. Depending on the needs and wants of each individual, transitioning may include both social and medical transitions; just one of the two; or for those who eschew gender completely, neither.