Dr Cass told BBC Radio 4’s Today programme that clinicians were concerned about having “no guidance, no evidence, no training”.

She said “we don’t have good evidence” that puberty blockers are safe to use to “arrest puberty”, adding that what started out as a clinical trial had been expanded to a wider group of young people before the results of that trial were available.

“It is unusual for us to give a potentially life-changing treatment to young people and not know what happens to them in adulthood, and that’s been a particular problem that we haven’t had the follow-up into adulthood to know what the results of this are,” she said.

We do not have longitudinal studies of how a very new drug, puberty blockers, impacts later development in adulthood. The drugs haven’t been around for long enough to test it. Makes sense that we should be cautious.