And, in case you're looking for a source, here's the updated guidance from the NHS.

From that doc:

"The interim Cass Report has advised that although there are differing views on the benefits versus the harms of early social transition, it is important to acknowledge that it should not be viewed as a neutral act. Dr Cass has recommended that social transition be viewed as an ‘active intervention’ because it may have significant effects on the child or young person in terms of their psychological functioning. In line with this advice, the interim service specification sets out more clearly that the clinical approach in regard to pre-pubertal children will reflect evidence that in most cases gender incongruence does not persist into adolescence; and that for 12 adolescents the provision of approaches for social transition should only be considered where the approach is necessary for the alleviation of, or prevention of, clinically significant distress or significant impairment in social functioning and the young person is able to fully comprehend the implications of affirming a social transition."