Folk are reading between the lines and have managed to read the opposite to what I said.
When I used the phrase "self-determination" I was referring to someone who claims to be trans not being forced into medical treatment against their will!
Therefore regarding seeking treatment, that should be a matter of self-determination. If someone seeks medical help because they consider themselves trans that should be available. The medical treatment should of course be appropriate (hopefully based on good evidence) and should - like any other medical treatment for either a "mental" health issue or "physical" health issue - be ethical, regulated and controlled by the appropriate medical practitioners.
I think the confustion came in when you responded to my statement
"In the US, there is effectively no impediment to medical transition once someone reaches their 18th birthday, and trans rights activists want it that way."
And you responded starting with
"Don't
you want it that way as well?" (emphasis in original)
I think that I, and lots of other people, thought that your comments about self determination were related to that response.
As noted earlier, my answer to your question is "No, I do not want it that way."
Based on your subsequent writing, it would seem that you want "regulations, ethics and controls for all medical partitioners", and providers of gender affirming care (i.e cross sex hormones and the like) should therefore be governed, by regulations, ethics, and controls.
You also emphasized that I was saying the same thing you were by saying, "All you are saying is that there 'should be regulations, ethics and controls for all medical partitioners' - which is what I said...."
So, if you and I are saying the same thing, it would seem we both agree that there should, in fact, be impediments to receiving gender affirming care. As I put it, in the post to which you were responding with the quote above, it's ok to make people "jump through some hoops".