If your child says they are transgender-
Hello. I am trans. I have transitioned and not reverted, so I feel transition is an option which may improve someone’s life. I won’t say it is the answer to all problems. I am not a parent, and I don’t know what you are going through. But I want to give a friendly perspective. I understand if you fear the thought of your child transitioning, and I agree that it may be wrong for them. If it is wrong for them, you want to protect them from the harm it could do, and so do I. But how?
Say your teenager objects when you call them your daughter. (Do you mind if I use neutral pronouns?) They want to bind their breasts and use a male name. They want to take hormones, and have surgery. Don’t worry too much yet. Getting surgery is a long road. They can change their mind right until the moment the anaesthetist starts the gas. What matters is what they do today. You need to know what they are doing.
My advice is to support your child’s decision. That means they can’t rely on you to protect them from it: if transition scares them, they have to protect themself. If you treat them like an adult you force them to behave like one. If you are cautiously supportive they will talk to you. They won’t transition as an act of teenage rebellion, and regret it later, because you don’t give them something to rebel against. You might persuade them not to get hormones over the internet- you don’t know what is in those pills- but seek proper medical evaluation.
If your child wants to bind their breasts, buy them a binder. The advantage of this is that it confronts the child with the reality of their decision. It is like a very tight sports bra: it does not do permanent damage, but is uncomfortable. If your child wants to transition to expressing female, you might even suggest facial electrolysis. That is painful, and takes a long time before the beard is significantly damaged.
Use of a different name is not much more extreme than the ordinary teenage exploration of their world, testing boundaries, discovering their feelings. Unless unhealthily constrained, teenagers play with identities and responses to find what works for them. Teenagers have always shocked parents. Let them play. You can’t protect them forever.
Please consider the possibility that transition is right for them. Of course it is completely wrong for most people. They will be unable to have children. They might never pass completely as the expressed gender. You can discuss these disadvantages with them calmly and without fighting, if you admit the possibility that transition might be right for them.
Of course girls should be supported if they are natural leaders or if they want to study engineering. Not every girl who kicks a ball or climbs a tree is a trans boy. Where it does not fit their personality, boys should be protected from macho culture- they can be feminine men. But for a tiny minority, transition is right. You do not want them to be miserable and directionless in their twenties, then transition in their thirties, and find it was right for them all along.