In an unprecedented move, hundreds of children are poised to participate in the first NHS-supported trial involving puberty blockers.

The groundbreaking study has drawn both interest and controversy as it plans to involve up to 226 children, some as young as ten years old, who identify as transgender.

Participants will receive injections of puberty-blocking drugs to assess their potential safety and effectiveness in aiding young individuals to physically align more closely with their self-identified gender, as opposed to their birth-assigned gender.

Researchers have refuted claims that the study could pressure children into taking medication that might impact fertility, bone density, and brain development.

They emphasize that the trial has been meticulously designed for safety, incorporating the most rigorous protocols with comprehensive monitoring to manage and evaluate any side effects or risks.

Despite these assurances, critics have called the study’s initiation “outrageous” and are demanding its immediate cessation.

Sources also suggested that some gender-critical groups could launch a judicial review against the trial in a bid to halt it.

Whether or not children should be allowed puberty blockers has been at the centre of several pro-trans protests in London and other UK cities 

Pro-trans activists have taken to London streets several times in recent years to campaign for more rights, including allowing children to take puberty blockers 

 Maya Forstater, CEO of sex-based rights charity Sex Matters, said the new NHS-backed clinical trial was ‘outrageous’ 

Maya Forstater, CEO of sex-based rights charity Sex Matters, said: ‘It’s outrageous that a trial involving yet more children being given puberty blockers has been given the go-ahead before studying outcomes for those already treated.

‘These drugs are a major intervention, with no evidence to suggest that they do any good and increasing reason to think they cause permanent harm.

‘It’s both foolish and unethical to expose yet more children to experimental treatment.

‘At this point, the only reason to research puberty blockers is to be able to offer long-term medical support to those who have already been exposed.’

Stephanie Davies-Arai, founder of Transgender Trend, a parent-led campaign group concerned about the rise in young people wanting to change gender, said: ‘We’re very disappointed that the trial is going ahead and we don’t understand how it managed to get approval.

‘We don’t think it’s ethical to give irreversible treatment to children where we don’t have adequate evidence of benefit, but we do know some of the risks.

‘Those are serious risks to fertility, bone density and brain development in adulthood.’

Plans for the trial were announced in 2024 following the publication of the Cass Review, which concluded that the quality of studies claiming puberty blockers have beneficial effects was ‘poor’.

It recommended ‘a full programme of research should be established to look at the characteristics, interventions and outcomes of every young person presenting to the NHS gender services.’

Puberty blockers were since banned from being prescribed by the NHS.

Before this, they were given to hundreds of children who were treated at the NHS’s controversial child transgender, the Gender Identity Development Service (GIDS) at Tavistock and Portman NHS Trust in London.

The Cass Review criticised the Tavistock clinic for leaving young people ‘at considerable risk’ of poor mental health and distress.

The youngest patients in the study, being led by researchers at King’s College London, will typically be ten to 11-years-old for girls and 11 to 12 for boys. The maximum age will be 15 years and eleven months.

Dr Hilary Cass said in her Cass Review that the quality of previous studies claiming puberty blockers have beneficial effects was ‘poor’

Stephanie Davies-Arai, founder of Transgender Trend, a parent-led campaign group concerned about the rise in young people wanting to change gender, said she was ‘very disappointed’ the NHS-backed trial was going ahead

One group of 113 will be given puberty blockers for two years, while the other half will be given the drugs after a one-year delay.

Both groups will be followed up for two years, meaning it will be four years before any results are published.

Children who take part will need the permission of their parent or guardian and an official diagnosis, according to World Health Organization standards, that they’re suffering from ‘gender incongruence’.

The puberty blockers will be administered by injection and will likely be Triptorelin, which has been in use and licensed since the 1980s to treat people who need to delay puberty because they start it earlier than normal.

However, other drugs may be given if any children have side effects. It will likely be injected every six months.

Researchers said each participant will have a series of health checks before taking part.

Chief investigator Emily Simonoff, professor of child and adolescent psychiatry at KCL’s Institute of Psychiatry, Psychology and Neuroscience (IoPPN), controversially said some children who take part could remain on the drugs after the study ends despite them being banned.

She added: ‘At the end of the trial, each young person will be reviewed individually and clinically to look at their ongoing care needs, which may include remaining on puberty suppressing hormones, if that’s deemed clinically appropriate for them.’

She denied the study amounted to ‘coercion’ and in an apparent reference to the Tavistock clinic, added: ‘One might want to argue that puberty suppression should never have been made available to people outside of the clinical trial some ten or 15 years ago.

‘The most ethical thing to do would have been to do a trial at that time.’

She insisted that there were ‘high levels of uncertainty about the balance between benefits and harms’ of taking puberty blockers and said this justified the study.

It will be funded by NHS England and is backed by King’s College London and the South London and Maudsley NHS Foundation Trust. Around five to six children will be recruited every month from the beginning of the New Year.

A second trial will run alongside it which will involve around 100 people jabbed with the blockers, comparing them to people who haven’t been jabbed for potential brain side-effects.

The studies have been approved by health regulators. They are part of a wider group of six studies costing the NHS £10.7million.