a gender identity disturbance in which a person with the reproductive makeup of one sex has a psychological urge to belong to the opposite sex; some people with this condition elect to undergo surgery to modify the sex organs to mimic the opposite sex, such as a male getting breast implants and an artificial vagina or a female getting a mastectomy and an artificial penis; male-to-female operation is more common because of better genital reconstruction results; hormone treatments help produce desired secondary sexual characteristics.