The question needs to be more specific.
Transition is simply the process of changing from living as one gender to living as another.
Not all transitions involve medical interventions.
Some people simply change their gender markers, i.e. their name and pronouns, and their gender expression, e.g. their manner or style of hair and dress.
I have no issue with hormone suppressors. They are not harmful and are completely reversible.
I am more cautious about cross hormone therapy, and conservative with regard to sex reassignment surgery, but am comfortable that the appropriate safeguards are in place.
One must be clinically diagnosed as transgender in order to begin cross hormone therapy or to receive sex reassignment surgery, and SRS is not performed on minors.
While I think gender, or the sense of one of whether he is a man or a woman, is something he knows at an early age, I also think that some gender non-conformity, particularly among lesbian, gay, and bisexual youths is normal, so people should be careful in assigning children as transgender.
For example, many lesbian, gay, and bisexual youths report being romantically attracted to members of the same sex at an early age. And because they live in a heterosexist society, they receive the message that one should be attracted to members of the opposite sex.
Some will try to reconcile that message with their attraction, and briefly entertain the idea that they should be of the opposite sex. However, most will quickly realize that they like their birth sex, and they just happen to like others of the same sex.
Transgender people may see that child and think he is trans, whereas lesbian, gay, and bisexual people may see that child and think he is gay or bi. So it is important to take the child for who he consistently and persistently purports himself to be, instead of imposing an identity upon him.