Is being transgender considered a mental illness?

I think it has a neurological and hormonal basis to being trans. Short and medium term studies have shown that transgender individuals seem to have a brain morphology that is closer to the average for the opposite sex rather than their birth sex. I think it also has to do with inverted sexuality. Gender dysphoria is no joke. It sucks that the only way to treat it currently available is social and medical transition. I mean if there were a pill or something people could take to combat gender incongruence I’m sure they would much rather do that than medically transition to alter their hormones and physical appearance to resemble the opposite sex. More research needs to be done into transgenderism and its causes. And it’s not as prevalent as society is seeing it right now. Rapid onset gender dysphoria is a social contagion. What treatment can best serve the small minority of people who really need help and cause the least amount of harm?