@PlanetJanette I can't think of a single other procedure which is comparable to gender affirming treatment, for a variety of reasons.
Firstly, although I believe gender dysphoria is no longer officially classed as a mental health disorder and that to suggest that it is one is now considered offensive to many trans people, it is still the case that these treatments are physical treatments, designed to bring about physical changes in the body, to treat a condition that only exists in the mind (the feeling that one should have been born in an opposite sexed body). Before undergoing hormone therapy or surgery, trans people might be incredibly distressed, but their bodies and reproductive organs are ordinary and unremarkable. After the hormones and surgery, the trans person may or may not feel happier from a psychological point of view, but their bodies are objectively less healthy than they were before. Anyone who has undergone "bottom surgery" is now permanently infertile. Anyone who has undergone a mastectomy will never be able to breastfeed. They may be completely fine with this, welcome it even, but from objective standpoint their bodies are less functional than they were before and the risk of side effects and complications is high. I cannot think of a single other medical procedure where the treatment for a problem which only exists in the mind is to cause deliberate damage to the previously healthy body. That makes gender affirmation treatment unique in this respect.
I would argue that this distinction stands even when compared with cosmetic surgery. Whilst you can argue that someone with body dysmorphia has a problem which only exists in their mind (e.g. their nose is too crooked or their breasts are too small and this is causing them distress), there is still an identifiable physical "problem" which the surgery aims to correct.
That said, I do think that some cosmetic surgeons are also failing their patients. I believe that Katie Price's surgeons, for example, have failed in their duty of care towards an obviously mentally unwell woman by continuing to perform ever more drastic surgeries on her.
And here we touch on the intersection between transgender healthcare, cosmetic surgery and mental health comorbidities. As other posters have noted, the fact that such a disproportionate number of people identifying as trans have either diagnosed conditions such as autism or ADHD, eating disorders, substance abuse issues, are same sex attracted, have been abused and/or have grown up in the care system should give us pause for thought. More than that. It should make us slam the brakes on and only proceed with the very greatest caution. If a patient presenting as having a transgender identity has none of the above issues, if, during multiple sessions with an experienced and diligent professional who is satisfied that none of the above things apply to this person and that the only "problem" is their gender dysphoria, OK, let's discuss how best to alleviate that. But if even one or those red flags is present, the focus should be on getting right to the bottom of that and getting the patient help for that, before the gender identity issue is addressed.
But this is not done. In some countries it is even illegal, considered to be conversion therapy, and only the affirmative approach is permitted. This is clearly a huge safeguarding failure.
Even professionals operating within a system where proper explorative therapy is allowed, often there is a race against the clock because the patient is a child who is preoccupied with getting hormone treatment before they have gone through the "wrong puberty" and their life is ruined forever. No therapist wants to be the one who took five years to diligently work through all a patient's issues and eventually conclude that yes, they really are transgender and the best course of action is hormones and surgery, only for the patient to turn round and say, "Well fuck you very much. You're only telling me what I told you when I was 12, except that now I'm 17, I've gone through puberty and have no hope of ever passing now. Thanks for ruining my life."
And that leads us to the final way in which this treatment is not comparable to any other treatment, in that the patients are usually very young. In the case of patients seeking puberty blockers, they may still be primary school age. Very few will be over the age of 25 or so, which is the age the prefrontal cortex is more or less fully developed. So these patients, as a class, and even without any mental health comorbidities, are more vulnerable than most other patients due to their age. That's not to say that a woman in her 40s seeking a fifth breast augmentation can't be vulnerable. Of course she can be. But she might not be. She might know exactly what she wants and understand the consequences of her decision, including all the possible negative outcomes. But the vast majority of transgender patients ARE vulnerable, simply due to their age. If a minor were undergoing any other kind of experimental treatment it would ultimately be up their parent or guardian to inform themselves, weigh up the risks and the benefits, and make a decision on behalf of the child. But because what we are talking about here is the child's subjectively experienced gender identity, the usual rules do not apply. In addition, different roles may be played by their parent, depending on the circumstances and where they live. Some minor patients might have a parent who is actively pushing them towards being transgender, e.g. sad cases like Jackie Green. Alternatively, some minor patients might live in a country where their parents are literally banned from trying to talk them out of it, at risk of them being taken into care. Again, no other area of medicine is really comparable here.
So yes, in my view anyone claiming a transgender identity should, on the basis of the large and growing body of evidence available, be considered vulnerable until proven otherwise, and heightened safeguarding should be in place.