Minimum age of 11 set for UK puberty blocker trial

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Gender-questioning children will have to be at least 11 years old to take part in a clinical trial assessing the risks and benefits of puberty-blocking drugs.

The planned Pathways Trial was paused in February 2026 after the Medicines and Healthcare products Regulatory Agency (MHRA) raised safety concerns and suggested introducing a minimum age of 14, where none had been set previously.

It says discussions with the research team have allowed “a number of safeguards”, including participation age, to be strengthened.

The first children are expected to be recruited in August, although ongoing legal action by some clinicians and campaigners questioning the trial’s safety and ethics, may delay that.

Puberty blockers for people under-18 questioning their gender identity were banned in 2024. The drugs, also known as puberty suppressing hormones (PSH), are used to delay or prevent puberty happening.

Researchers from King’s College London have also agreed not to recruit participants until after 1 August, to allow for legal proceedings to take place.

No child would be able to take part in the trial without parental consent and young people will continue to need to meet all the other eligibility criteria including “demonstrating a good understanding of the intervention and its possible benefits and risks”, they add.

The researchers say they “always welcome scrutiny” of studies involving children and young people, and that in addition to setting a minimum age they have strengthened patient information. But “there are no major changes to the design or conduct” of the trial.

They say the new age limits are 11 for “birth-registered” female participants, and 12 for “birth-registered” males.

Clearer guidance is also being introduced about when the drugs should be stopped, for instance, if there are concerns around bone density, impact on brain function or vaginal bleeding. More detailed information will also be provided on how individuals can preserve their fertility.

The Pathways Trial, approved by UK regulators and ethics experts in November 2025, is set to involve children under the age of 16 who are distressed about their gender and currently accessing gender services.

It would examine the impact of the drugs on their physical, social and emotional wellbeing.

Some doctors have questioned whether the trial is necessary. Campaigners are also taking legal action against the MHRA, the government and others involved in the trial. They claim it is unethical and that children cannot give fully informed consent to a treatment that might affect their future fertility.

A 2024 review by Dr Hilary Cass found gender medicine had been operating on “shaky foundations” when it came to evidence for treatment, with the ban for puberty blockers for under-18s introduced after the review had raised concerns about their safety.

Cass has since told the BBC it is “vital” that the trial for puberty blockers for under-16s goes ahead, or “we’re going to have ongoing charlatans just handing out inappropriate drugs”, pointing to the private sale of the drugs – particularly online.