Remember me
Patient information sheets given to parents and children who are considering participating in an NHS-backed puberty blocker trial do not provide a clear or accurate account of the balance of risks and benefits of puberty suppression, a group of healthcare professionals argue.
The Clinical Advisory Network on Sex and Gender (CAN-SG) – a coalition of more than 100 clinicians and medics – contends that without this type of evidence-based guidance on the risks of involvement, parents cannot provide truly informed consent, and that the children and young people in their care therefore should not assent to participation.
The new trial is part of a group of research projects called Pathways (Puberty Suppression and Transitional Healthcare with Adaptive Youth Services) aiming to provide high-quality evidence to help inform and improve the care given to children and young people attending NHS gender services. It’s run by a team at King’s College London (KCL), with the trial due to start this month (January). However, KCL has confirmed to the New Statesman that recruitment to the trial has not yet begun.
A clinical trial of puberty blockers was one of 32 recommendations made by Hilary Cass in an independent review of NHS children’s gender services. But ever since a new trial was confirmed in November 2025, debate over whether it is ethical to begin another study of puberty blockers has been fierce.
New year, new read. Save 40% off an annual subscription this January.
Public opinion appears to be against it. Polling by Whitestone Insight showed the majority of adults were not in favour, including among both current Labour supporters and those who voted for the party in the 2024. The government faces a legal threat calling for the trial to be stopped.
More than 380 clinicians, including some who specialise in evidence-based medicine and have helped write national clinical guidelines, have written to the Health Secretary Wes Streeting expressing their disagreement that the trial should take place in its current guise, or before other less invasive research avenues have been pursued first. The signatories, which include 220 doctors and surgeons, expressed “grave disquiet”.
Some are experts in trial design who are critical of this particular trial’s approach. Others believe no trial could be ethical, among them clinicians who worked with children at Tavistock’s Gender Identity Development Service (Gids), which closed in March 2024.
Now, some of these professionals are raising alarm over the patient information sheets given to parents and children. The sheets are meant to provide detailed information about the potential risks and benefits to participants in any medical trial.
Speaking in committee room 3 of the House of Lords on 15 January, Dr Louise Irvine, co-chair of CAN-SG, told gathered journalists: “Parents have not been told the true likelihood or the full scope of the harms involved.”
Nowhere are parents told of the possibility that their children might feel differently about their gender identity in the future, that there is no reliable predictor of which children might benefit from pubertal suppression, or that they could possibly regret medical steps taken when they were younger. Irvine argued that risks to bone health, sexual function, brain maturation, identity development and fertility were also not adequately reflected in the information sheets.
“The Pathways Patient Information Sheets treat puberty blockers as though they were a standalone, reversible pause,” Irvine argued. This characterisation was “misleading”, she added. “In reality, more than 90 per cent of children who start puberty blockers go on to cross sex hormones.” She urged the press to read them for themselves. The New Statesman has done so.
Cass has publicly supported the Pathways trial, saying in November she was “really pleased” the trial was going ahead. “Given that there are clinicians, children and families who believe passionately in the beneficial effects [of puberty blockers],” she said, “a trial was the only way forward to make sense of this.” Yet those concerned about it cite the findings of Cass and her team’s review as reasons to be cautious about the trial. This publication did the same in its detailed analysis of the trial’s design and stated aims.
The trial information sheets say that puberty blockers may provide young people with gender incongruence “time to explore their gender identity without worrying about their body starting to change”. Parents and children are not told how speculative this hypothesis is, nor that it was rejected by the Cass Review. “Given that the vast majority of young people started on puberty blockers proceed from puberty blockers to masculinising [or] feminising hormones, there is no evidence that puberty blockers buy time to think, and some concern that they may change the trajectory of psychosexual and gender identity development,” Cass wrote in the 2024 review.
One study, started by the Tavistock Gids and University College London Hospitals in 2011, found that 98 per cent (43 out of 44) of children aged 12-15 taking part progressed from puberty blockers to start cross-sex hormones (testosterone for females wishing to masculinise and oestrogen for males wanting to feminise). Gids staff working with gender-distressed children were presented with similar statistics in 2016. One, Dr Anna Hutchinson, described it as her “holy fuck” moment. And a wake-up call for many of her colleagues too.
Back then, clinicians saw that this data had profound implications for consent. It wasn’t just that families and young people needed to be told about blockers: they also needed more information on what transition might entail. “You couldn’t do it after you put them on the blockers,” Dr Natasha Prescott told me while I wrote Time to Think, “you had to do it before.” Because “once they’re on the blocker, they’ve started along a path”.
In later years, a group of independent health professionals – brought in to provide additional oversight of Gids’ puberty blocker referrals – insisted children could not begin treatment without the expectation of progression to hormones being “adequately discussed and understood”. This “Multi-Professional Review Group” (MPRG) was introduced in 2021, following NHS England and Care Quality Commission concerns about Gids.
Perhaps most striking in today’s context is that the Health Research Authority (HRA) – the body responsible for ensuring the quality of the patient information sheets – has itself previously warned against describing puberty blockers as providing “breathing space”. In its 2019 investigation into the Gids early intervention study, the HRA advised staff working in gender clinics to “avoid referring to puberty suppression as providing a ‘breathing space’, to avoid risk of misunderstanding”. Instead, the investigation argued, they should be seen as an aid to future medical transition.
The children taking part in the 2011 Gids study had been “carefully selected”, chosen because of their long-standing distress around their gender identity, the HRA noted. The new Pathways trial similarly claims that only a small minority of children with both a stable gender identity and home life, and who clinicians believe will “benefit” from puberty blockers, will be eligible to take part. It’s unclear, therefore, why the same HRA rationale would not apply equally to the new research.
Parents who have already faced the difficult decision over whether to agree to their distressed children’s puberty being blocked are raising similar concerns. The New Statesman has seen a lengthy, forensic letter sent to the HRA on 15 January by a concerned clinician and researcher, who is a parent to a trans-identified child (who is not part of the Pathways trial). Having “been faced with pressure to agree to such medication in a context of similar inadequate information”, the sender explains they did not want others to do the same.
The letter, written with the help of “several colleagues” and now being handled as a formal complaint, claims not just that critical information is missing, but that the information sheets as currently written violate the HRA’s own requirements. Any research involving the NHS must be approved via one of the HRA’s independent Research Ethics Committees (REC). The REC is then responsible for granting both ethical approval for the trial as a whole, and for ensuring that information sheets allow for informed decision-making. HRA guidance states that in order to facilitate this, researchers “must state clearly what the risks and benefits of your study realistically are”.
The King’s College London research team was questioned by the REC on 4 September 2025 on the effect of puberty blockers, as approval was sought for the Pathways trial. Might, the ethics committee asked, “blocking the normal biological process of puberty via the study drug… change the participants views, or prevent further development of their views, on self-identity”? The research team responded that it was “acutely aware of this”. The researchers were advised to make the impact of the drug “clear in the PIS [patient information sheet]”. The information sheets do not reflect the risk that treatment with puberty blockers may in itself “lock-in” – to use Cass’s term – children and young people to a pathway ending in medical transition.
Asked whether the patient information sheets allowed parents and children to make a truly informed decision, a spokesperson for the HRA, said: “The Pathways trial was reviewed in line with well-established legal and national policy frameworks by a properly constituted Research Ethics Committee (REC) for clinical trials.”
There is an “established and thorough process for how RECs review information for study participants”, they continued, which ensures “information provided is as clear as possible” and key points are “easily understood”. “This includes explaining potential risks and benefits that are relevant to the study in review. RECs cannot consider wider issues or concerns which are beyond the scope of the study being reviewed,” they added.
There are multiple other weaknesses in the information provided to parents and children, concerned professionals represented by the CAN-SG maintain. According to Irvine, the information provided “ignores or minimises critically important risks identified in the Cass Review”.
When Cass first recommended research into puberty suppression for gender dysphoria in July 2022, for example, she warned of potential “longer-term neuropsychological consequences” with using the drugs. Brain maturation, she said “may be temporarily or permanently disrupted by puberty blockers, which could have significant impact on the ability to make complex risk-laden decisions”. In the Pathways trial information sheets, that risk is represented like this: “There are also concerns that GnRHa [gonadotropin releasing hormone analogues, the puberty-suppressing treatment] might affect brain development and learning, based on findings from animal studies.”
Risks to both bone health, which – according to academics undertaking a systemic review of all the evidence available – is “compromised during puberty suppression”, and sexual function are not explored adequately in the patient information sheets either, Irvine said.
The KCL Pathways research team told the New Statesman the trial had gone through “the normal rigorous process of independent ethics scrutiny” and that, “in line with HRA standards on informing participants and seeking consent, our materials set out the study purpose, design and what is known and unknown about puberty‑suppressing treatment.”
But it is the major risk to children’s future fertility from puberty suppression, where there is perhaps the greatest mismatch between what is known and what is contained in the patient information sheets. And this is linked intrinsically to the fact that, as the 2011 study – and other international studies – suggested, almost all children move from puberty blockers to hormones.
In the 26-page information sheets, the risk to children’s future fertility is mentioned across five lines. Parents of potential trial participants are told that “it is important that your child talks to the doctors in the clinic about the options they have for their fertility in the future”. These include egg or sperm storage, the leaflet adds.
But there is no explicit explanation as to why this should be so. When the same drug planned for use in the trial is prescribed for precocious puberty (when children begin puberty too early at very young ages), the information leaflet does not advise fertility preservation. The greatest risk to fertility from puberty blockers, when used in the very different context of gender medicine, is brought about by the likely progression from blockers to hormones. When puberty is suppressed in the earliest stages, and then followed by masculinising or feminising hormones, there is no opportunity for children’s eggs or sperm to mature. “For those children, fertility preservation would require stopping puberty blockers to allow gamete maturation for collection,” Irvine explained.
Pathways researchers said that they would continue to keep participant information under review throughout the trial. “Beyond the patient information leaflets,” the team explained, “the young person and their parents/legal guardians must be able to show that they fully understand the possible benefits, risks, and long-term effects of treatment. This understanding is developed through a series of detailed discussions with clinical specialists in the new gender services and those who have expertise in hormonal interventions.”
Fertility preservation “is presented in an unrealistically optimistic way”, Irvine added. Even for children who had reached a later stage of puberty and had viable gametes to store before joining the trial, it remained an “invasive and difficult process”, she said.
There is no data on what impact – if any – blocking puberty for several years into later adolescence might have on future fertility, should that young person choose not to take hormones. In part, this is because so few children have done this.
A Department of Health and Social Care spokesperson said that “young people with gender incongruence need access to high-quality, safe and effective care” and it was “following the Cass review, which was clear that the evidence on care for these children is lacking, and proposed this research to help provide it”. The spokesperson said children received “a range of guidance beyond these information sheets through detailed discussions and rigorous checks with clinicians over a number of months” and this included conversation on detransition.
[Further reading: One in ten children receiving NHS gender care are self-medicating with sex hormones]
Content from our partnersRelated
Comments (0)