A transgender person is someone who happens to possess the unambiguous reproductive system of one gender, but feels that he or she belongs with the opposite gender. She doesn't choose to be transgendered, the transgender drive chooses her.

The hardwired trans-brain

In terms of the M to F transgendered patient only the patient herself understands transsexuality. Everyone else is a mere observer. Transsexuals are clearly a mixed group and each subgroup appears to have its own underlying mechanisms as well as its own particular nature. Consequently our comments have to be generalizations.  For many years, transsexuality was considered a psychological aberration and many early recommendations for transsexual treatment such as the Harry Benjamin protocol were based on this false assumption.  It is now clear that transsexuality is biological, its dictates hardwired into the brain. The source of this hardwiring appears to be a genetic mutation involving changes in the androgen receptor such that testosterone has anomalous effects on the brain. The likely target for these effects is those parts of the brain involved with obsessive-compulsive disorder and body dysmorphic disorder.  The n bottom line is that the programs for self-identity say female whereas the anatomy is definitively male.  Effective hormone therapy is the only effective road to reconciliation between the two. 

The terms "transgender", "transsexual" and gender dysphoria should not be used interchangeably. Gender dysphoria is a description of the mental symptoms that transgender patients experience as a result of the transsexual drive, particularly when the patient is prevented from feminizing.  It is a mental symptom complex, as opposed to a behavioral drive, which is what transsexuality is.