what do you mean what parts?
Counselling and therapy are usually the first and continuous line of defense.
Then there’s social support structures built around them and they have duties to perform like living for a year under an assumed name and identity and dress.
and there’s
puberty blockers for adolescents if needed
adding hormone for young adults once they’ve passed the various tests
surgery for adults once they’ve gone through even MORE years of therapy and counseling etc.