Gender dysphoria is a general symptom of distress typically experienced by transsexual people. There are two kinds of dysphoria, physical and social. Physical dysphoria is the discomfort they feel because their body feels wrong and doesn't match their gender identity. Social dysphoria is experienced when society (family, friends, others) doesn't treat them in a manner consistent with their gender identity.
Contrary to popular belief, gender dysphoria is not a mental disorder. As I described above it is a symptom of distress, That symptom is directly related to being born transsexual, that is with a gender identity in the brain that doesn't match the sex of the body. Researchers and scientists have established that transsexualism is a physical birth condition. So transsexualism is the birth condition and gender dysphoria is a symptom of it.
In addition the American Psychiatric Associations bible is called the Diagnostic and Statistical Manual (DSM). The DSM is split into two halves, mental disorders in one half and symptoms of distress in the other. Gender dysphoria is in the latter. Years ago transsexualism was categorized as a mental disorder, but like homosexuality before it, it was removed once the medical research proved that categorization was in error. Hence transsexualism is a physical birth condition and gender dysphoria is merely a symptom of that.
A primer on transsexualism that may help:
http://forum.beginninglifeforums.com/index.php/t/15139/22bed092ab66e4c1039dbc52659abf39/
Once a transsexual person medically transition to living in a manner consistent with their gender identity, the gender dysphoria they experience is dramatically reduced or even eliminated.
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參考: me-woman who was born transsexual (post-op)