I have no sources, but I've read it multiple times - Basically, we know that your chromosomes shape you in two "steps", one for the body (as in, genitals and stuff) and one for the brain. The theory is that something happens there and instead of turning the body male and the brain male, body becomes male and brain becomes female.
It is possible to see, in the brain, a part that tells you how your body "should" look like (for example, 2 arms, 2 legs, dick and no breasts. So your brain understands what you are and how you function). This part, for some reason (possibly the previous stated theory) does not match with the body.
Being transgender is a very real thing. I kinda suspect that there are (tumblr)people who claim to be trans without actually being it, and thats a shame.
I read a study where scientists had found a way to identify trans people at the age of 5 with 90% + certainty. However, early study and it might be coincidenses and whatnot, but still. And none of these things are determined through asking about a person's feelings, its brainscans and stuff.
If you're born with an extra leg or something, you'd most likely want that removed to make your body "normal" again. Being born transgender is similar, and physical treatment helps the same way.
