The NHS plans to offer puberty blockers in a £10.7 million clinical trial, despite their indefinite ban across the UK last year.
The drugs were banned in 2024 due to concerns they are unsafe and harm bone and brain development.
Under the planned trial, run by a team at Kings’ College London, children seeking help from NHS gender services could receive the drugs if parents and doctors agree.
The “Pathways” trial will monitor participants for two years, including regular brain scans.
The NHS plans to offer puberty blockers in a £10.7 million clinical trial, despite their indefinite ban across the UK last year
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The trial is yet to pass ethical approval, although the NHS expects it to begin this year.
Puberty blockers suppress the release of sex hormones to pause physical changes of puberty, such as breast development or facial hair.
Over the past two decades, they have been widely used around the world for children with gender dysphoria.
The NHS-commissioned study is due to last until 2031 and was confirmed by the National Institute for Health and Care Research on a contract worth £10,694,902.
The research will track the well-being of children attending new NHS gender clinics, including those not on puberty blockers.
It will also monitor whether the drugs affect young people’s thinking and brain development.
In 2024, the NHS stopped using puberty blockers in response to the Cass Review, which found safety risks and “remarkably weak evidence” to support them.
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Dr Hilary Cass recommended a new trial to look into puberty blockers in her final report.
She has welcomed the new trial, saying it “aims to fill some of the gaps in our knowledge about the outcomes of different interventions”.
The trial would address “uncertainty about the impacts and efficacy of puberty-suppressing hormones”, according to Dr Cass.
The study is being led by Professor Emily Simonoff, head of child and adolescent psychiatry at King’s College London.
Several doctors and campaign groups have raised concerns about the ethics of the trial.
They argue existing evidence proves puberty blockers are harmful to brain and bone development.
Critics also warn about damage to long-term fertility and sexual function.
Under the planned trial, run by a team at Kings’ College London, children seeking help from NHS gender services could receive the drugs if parents and doctors agree
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Dr David Bell, a former whistleblower at the Tavistock trust, said he found it “extraordinary” that the NHS-supported trial was going ahead.
“Again an experiment is being carried out on children,” he said.
“If we accept that puberty blockers were an experiment that failed many many children, how can we justify conducting a trial when we know that a significant number of children will be harmed?”
Dr Bell raised specific ethical concerns about the trial’s approach.
“There are a number of reasons why it is unethical. Once children are started on puberty blockers it’s extremely hard for them to come off them,” he warned.
One psychiatrist warned the trial risks “repeating the same ethical failures” of the now-closed Tavistock gender service.