As I said, it makes sense to describe gender dysphoria as a mental health issue - but it's a special one because, at least in many or most cases, the people suffering from that can actually be given what they are longing for in a relatively straightforward way, hence permanently solving the problem.

Because gender dysphoria can be permanently cured by simply giving people what it is they're longing for, which doesn't do them or others any harm. You can't say that for any of the other things you mentioned.

Now, correct me if I'm wrong, but I would guess that you're perfectly aware of all this, the problem being merely that you consider gender reassignment surgery as automatically wrong and harmful even to people who hold it as their deepest heart's desire. In which case the reasoning does break down, but only because of your dogmatic position on the topic.

I said 'what makes you happy', as in happy in the long run, not 'what you feel like doing at a particular moment'. I think everybody is very, very clear that gender reassignment surgery isn't something you undertake on a whim after waking up one day and thinking it'd be fun to have another gender for a change.

Naturally as a Christian you would say there should be higher goals in life than even your happiness even over the long term - but then, it's not as if gender reassignment surgery would stop someone from adhering to such higher goals or from being a Christian, so it's not an either-or deal.