I recall in my psych class the classic story of the boy, one of twins, who was taken in to have his penis mutilated with the circumcision operation and the butcher botched it and destroyed the penis. So the parents agreed that the penis should be removed and the boy surgically altered to resemble a girl, and the parents raised him as a girl.
Success! Gender is not determined by chromosomes...well, not really. What really happened was that the mutilated boy wanted to be a lesbian, if you catch my drift and hated his life. He was a boy, just like in the old Who song.
And the forces driving many..most...of these sad people into self-mutilation is an abusive psychiatric industry and diseased cultures that applauds each act of self-mutilation as some kind of heroic step towards equality...rather than giving these people the help they need to come to terms with the fact that their feelings about their body aren't right and they need to re-adjust how they feel towards what they are, male or female based on their biology, rather than attempting a doomed-to-failure attempt to sculpt their bodies into what they aren't.
No wonder those duped people feel regrets when their pecker has been carved off to make an innie.