The view that I share with any patient considering a diagnostic exercise is, "will it change anything?"
Diagnosis as a precondition to therapy is, of course, essential. Diagnosis as a motivator for lifestyle changes (diet, exercise, etc.) is incredibly valuable. But diagnosis for its own sake I am much more ambivalent about.
In your case, I think diagnosis will fall into the "valuable" category. You are going to embark on a long process of change to align your physical body with your identity. How far you go down that road remains for you to decide, but during that process you will be relying on help an advice from a team of doctors including a psychiatrist. Knowing the totality of your circumstances will enable them all to give you better advice for your decision making.
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--James