A landmark review into young people's gender care, written by Baroness Hilary Cass, was published in 2024.

The government then banned the use of puberty blocking drugs in children's gender care across the UK. The drugs can pause the physical changes of puberty such as breast development and voice deepening.

Children already on the medication were allowed to continue but new prescriptions could only be offered as part of a controlled clinical trial.

NHS England commissioned the Pathways study to try to establish scientific evidence about the possible health risks and benefits.

Speaking to the BBC in June, Cass said that the trial was "essential" to answer the question about "whether these drugs are helpful or not".

KCL researchers have said they hope to recruit 226 children under the age of 16 who are already accessing specialist gender services in England and have a diagnosis of "gender incongruence", where a person's sense of their gender does not match the sex they were recorded as at birth.

The team has said any young person participating in the "carefully designed study" will undergo detailed medical and psychological assessments. They and their family will also have to demonstrate they understand the potential impact of taking part.

The trial will look at the effect of the drugs on bone density, brain development, fertility and mental wellbeing.

"High profile studies like this will always attract extra scrutiny and we welcome the opportunity to assure the public of the safeguards put in place," said Dr Matt Westmore, chief executive of the Health Research Authority, one of the defendants in the case.

"The checks that we carry out, alongside the independent ethics review process, ensure the interests of participants are put first, and that the research is safe and ethical."