Question about mental health

[general-motors.livejournal.com]

Does anyone know what could be causing a person to feel they're transgender? I mean if they "really" aren't? Could hormone imbalances cause this... or some sort of a mental illness? Obsession? How common would that be? What do you think? What kind of things they test you for?

I'm asking this because my doctor doesn't take me seriously and she's giving me a hard time trying to get forward with my process.

thanks.