Transgender youth are children or adolescents who do not identify with the sex they were assigned at birth. Because transgender youth are usually dependent on their parents for care, shelter, financial support, and other needs, and because most doctors are reluctant to provide medical treatments to them, transgender youth face different challenges compared to adults. There is a broad consensus among experts and professional associations that appropriate care may include supportive mental health care, social transition, and puberty blockers , which delay puberty and the development of secondary sex characteristics to give children time to make decisions about more permanent courses of action. In many parts of the world, being transgender  is not widely accepted by the public and as for transgender youth, they not only face discrimination but also can encounter family exclusion. To "come out", according to Merriam-Webster,  means to openly declare something about oneself previously kept hidden or to openly declare one's homosexuality.
Helping a Teen with Gender Dysphoria - Evolve Treatment Centers
Teenagers looking to transition often describe themselves as having been born in the wrong body. It is commonly acknowledged that while biological sex is genetically determined, gender is a social construct. A human being cannot—and should not—be reduced to their biology, or indeed their genitals, because psychologically we are as much a product of the way that other people treat us as we are of our genetic inheritance. Homo sapiens are social creatures: our ability to cooperate is what gave us the evolutionary upper hand over our stronger Neanderthal cousins. You would notice the physiological differences.
Teenage transgender row splits Sweden as dysphoria diagnoses soar by 1,500%
Transgender teen Theo Zachariah began identifying as trans at age 13, and now at 16, takes testosterone. At first, Miriam Zachariah's teenage nephew Theo, who was born female, came out as gay. But he "presented as very gender fluid," she says, which suggested that he hadn't made "a clear choice one way or another. Zachariah decided to ask her nephew, "Do you think you might be trans? A month later, at age 13, he began identifying as trans.
Or your child might use another term to identify their gender. And your child might discover or understand more about their gender identity over time. This might mean they express this identity in new or different ways. This might be through their name, clothes, behaviour, hairstyle or voice.