But the report had limitations, most seriously – as we said in our initial commentary – its failure to tackle the school-to-clinic pipeline and its endorsement of a trial of puberty blockers to provide the evidence base it recognised was lacking. The puberty-blocker trial was one recommendation of 32 in the report, and the only outright bad one. There was no detail on how such a trial might be designed; many experts thought it would never happen because ethical approval was simply not possible. 

And yet Baroness Cass has thrown her considerable prestige and authority behind plans, now far advanced, to carry out such a trial. Here is why we think she is wrong.

School-to-clinic pipeline

While Baroness Cass was carrying out her review, we raised the problem of the promotion of trans ideology and widespread acceptance of “social transition” in schools, meaning children were being treated as if they had changed sex in school rules and policies. Many parents say that it was in school that their child first picked up the idea that they might be trans, and it had become commonplace for schools to transition children behind their parents’ backs. The Cass Review acknowledged the role of social contagion in trans identification, and suggested that social transition might be unwise. But it showed no understanding of the pernicious way that doctors’ recommendations of social transition had been converted into a “doctor’s orders” edict to schools, which then extended to children being supported to socially transition in school without any doctor’s involvement. 

The review also failed to grapple with the fact that what an individual child wants is not a matter for them alone. Even if, hypothetically, puberty blockers and social transition are “right” for a particular child, this cannot be accommodated in schools without unacceptably infringing on the rights of other children. This means social transition supported by puberty blockers and the promise of cross-sex hormones cannot ethically be offered to a child as a viable and coherent package.

Schools exist to educate children while keeping them safe, not to provide complex and risky psychosocial treatments. A gender-confused child’s classmates are not there to validate the child’s professed identity by accepting the falsehood that he or she has changed sex. Doctors have no right to propose to their patients that this should happen, even if that is what those patients want.

The missing evidence base

As originally envisaged, the review was supposed to include evidence gleaned from following up the children who had previously been prescribed puberty blockers by the NHS, thought to be around 2,000 of those seen at the Tavistock. This “data-linkage study” would not have been definitive on outcomes because the control group (children seen but not treated) would not be statistically comparable with those who received the drugs. But it would have provided excellent data on safety, revealed whether the children were still distressed, probably provided useful information on desistance and detransition, and in general been the most meaningful data on outcomes from medicalising gender distress beyond a year or two anywhere in the world.

But the adult gender clinics refused to cooperate with the Cass review, and refused to hand over their data. In the end the review was published without that information. The data-linkage study is still nowhere to be seen. And yet in December 2024 the secretary of state for health, Wes Streeting, announced that NHS England was commissioning a new trial of puberty blockers. And in November 2025 news broke that the trial had received ethical approval. 

If the data-linkage study had concluded by now, it would have established the existence or otherwise of some of the most immediate harms thought to be caused by puberty blockers, in particular whether they raise the risks of early-onset osteoporosis, which is so rare among people in their teens or 20s that even a couple of cases would send a strong signal about treatment safety. It would also help establish whether puberty blockers are helpful in reducing suicides, which are also, thankfully, extremely rare at that age. By now we would have data on chronic and acute health problems, emergency admissions, diagnoses, prescriptions and eligibility for incapacity benefit for adults who had received puberty blockers as children, which would give a clear picture of whether or not they are thriving. 

In short, we would know a lot more about whether the treatment pathway that starts with puberty blockers and almost always continues to cross-sex hormones creates serious risks to physical health, and whether those who travel this path are unusually unhealthy in early adulthood. If the answer to either of these questions was Yes, any further use of these drugs would be indefensible.

Baroness Cass has repeatedly criticised the adult gender clinics for refusing to cooperate. She knows that puberty blockers are not a standalone treatment: her report said so. She knows they hugely increase the risk of future, irreversible medical intervention – that they do not, in the words chosen by journalist Hannah Barnes for the title of her whistleblowing book about the Tavistock, offer children “time to think”. Before the advent of puberty blockers most gender confusion resolved in childhood; afterwards, most persisted. Puberty blockers are an almost inevitable precursor to giving oestrogen to boys and testosterone to girls. Any fair assessment of their benefits, risks and harms therefore has to include those of cross-sex hormones. She also knows that the previous trial at the Tavistock clinic opened the door for routine prescribing before its results were published, and that those results belatedly showed no benefit for children’s mental health. 

The planned trial will compare answers to a questionnaire about wellbeing between children who receive puberty blockers at the start of the trial, and children who are required to wait a year. That can provide no useful information about medium- or long-term risks. It is likely to create an artificial difference between the trial’s two groups, since participants may well believe false claims by the trans lobby that puberty blockers are “life-saving”. Those who receive the treatment straight away are likely to be elated; those forced to wait devastated.

Recently, Baroness Cass has defended the trial as a harm-reduction measure. Children denied puberty blockers on the NHS, she says, may turn instead to online providers who do not monitor their wellbeing and may be selling less safe alternatives. But the trial has not been designed to test harm reduction. And no data is being collected to find out whether or not overall harm is in fact being reduced.

Despite all this, instead of putting her considerable authority and prestige behind the push for the data-linkage study, which would give useful information without exposing any more children to a treatment regarded as so risky that neither the NHS nor private health providers can lawfully prescribe it, Baroness Cass instead supports a new trial. That the new trial is so poorly designed that it cannot possibly provide a meaningful contribution to the evidence base her review said was lacking makes this even more inexplicable. 

Reckoning with the Supreme Court

In April 2025, a few months after plans for the new trial were announced, the Supreme Court ruled in the case of For Women Scotland (FWS) that in the Equality Act, sex means sex. Two weeks after that judgment was handed down, Sex Matters, together with LGB Alliance, Transgender Trend and Genspect, wrote to Sir James Mackey, then the chief executive of NHS England, and the health secretary. 

In that letter we spelled out the implications of the ruling for the care of gender-distressed children:

“Children under the care of all gender services, both NHS and private, must now be told that they will never be able to access spaces or services for the opposite sex, no matter what legal or medical steps they take now or in the future. Such children will, throughout their lives, need to use either the spaces and services designated for their own sex or an alternative provided for both sexes (mixed-sex or single-user) if available.

…

“We have always argued that it was unethical and a breach of human-rights principles to treat young people’s mental distress with major, unproven physical interventions with known harms (including to their adult sexual function and fertility), and to promise them that they could intrude on other people’s privacy, safety and dignity as well as put their own safeguarding at risk by using spaces for the opposite sex. 

“Now that the Supreme Court has ruled out the use of opposite-sex spaces, no promise can be made that medical treatment will enable a person to fit in or go unnoticed while using opposite-sex facilities. The use of these drugs on children too young to understand this is ethically untenable.”

This year Keeping children safe in education, statutory safeguarding guidance for schools, has been updated to take account of the judgment. Schools have been expressly warned that by law they must record every child’s sex accurately, and must not ever allow any child to use toilets (or changing-rooms where they exist) for the other sex. Even if a school considers using preferred pronouns for trans-identifying children, or allowing them to wear the opposite sex’s uniform (we think both these policies are indefensible on safeguarding grounds), it is now beyond doubt that schools cannot lawfully pretend any child is the opposite sex.

As we also said in that letter, this undercuts the entire rationale for treatment with puberty blockers:

“The drugs are intended to block gender-distressed children’s natural puberty so that if they persist in cross-sex identification and progress to cross-sex hormones and perhaps surgery, they will “pass” better as the opposite sex. But passing as the opposite sex ceases to be a desirable goal to present to children when they will never be permitted to use spaces or services for the opposite sex, and may in future be restricted in employment in roles such as police officer or nurse which can involve intimate contact with others in situations where sex matters for those others’ human rights. Instead it becomes a major, permanent social problem for those young people, since their future lives and freedoms will be seriously curtailed by being legally barred from using the other sex’s spaces while appearing anomalous in those for their own sex.”

Not only are puberty blockers a treatment based on a false premise, but they cannot ethically be offered to any child. Quite apart from the health risks, no child (or parent on their behalf) can consent to destroying their future ability to live normally in society as an adult. 

As we wrote when news broke last year that the trial had received ethical approval:

“The Department of Health, NHS England, the National Institute for Health and Care Research and the Research Ethics Committee which approved this study have allowed it to go ahead by ignoring the conflict with the Equality Act and feeding the unrealistic hopes of children who are not old enough to understand or consider these constraints on their desires.

“Recruiting children into a study that is based on a mis-selling of rights and which forecloses their chances for adult sexual function and fertility is unconscionable.”

That a clinician and parliamentarian of Baroness Cass’s stature continues to press for this trial risks undermining all the good work she has done.

The post Baroness Cass is wrong about the puberty-blocker trial appeared first on Sex Matters.

These debates are the chance to discuss an issue. A government minister is present to hear and respond to the debate and there is a vote at the end, but there is no decision to be made. 

Read a full transcript of the debate or watch it on parliamentlive.tv.

Opening comments

The debate was opened by the chair of the parliamentary petitions committee, Jamie Stone MP. He said: 

“The petition raises two main areas of concern: the possible long-term medical side effects of puberty blockers, and whether meaningful consent can ever be obtained from a child or adolescent.”

Despite this, he sought to balance the horror of healthcare disasters like that experienced by Keira Bell by citing another transitioner whose experience with puberty blockers, he said, was “profoundly positive” and who had “experienced no negative health outcomes”. He said that: 

“For her, being forced to undergo male puberty would have been the greater trauma. She is one of many who report that their lives have been significantly improved by timely support.”

Four MPs intervened during the opening speech, two Labour and two Conservative, all with pithy points for the petition. Tonia Antoniazzi pointed out that the survey being used in the “Pathways” trial asks questions like: “Have your parent(s) treated you fairly?”. She wondered how her son aged 11 would have answered that. Since any child at that age would probably say No, she felt the questions were not fit for purpose. 

Graham Stringer challenged Stone’s framing of the issues as complex, saying: 

“It is actually quite simple: we should not be experimenting on children, particularly as we cannot do double-blind experiments. Those are two fundamental reasons why these so-called experiments should not go ahead.” 

Stuart Anderson said that his own children constantly changed their minds about things, and that he could see no justification for experimenting on children: 

“What might be a short-term solution could become a permanent solution that people often grow to regret.” 

Sir Julian Lewis asked about the data from all those children previously treated at the Tavistock’s Gender Identity Development Service (GIDS), saying surely no more children should be treated with these drugs until that data had been explored. 

Twelve MPs spoke for the petition

Speeches from backbenchers were limited to two minutes each. This meant there really could be no debate, because speakers short of time refused to give way to interventions. Twelve spoke for the petition, against the trial going ahead, and six spoke against the petition and for the trial. 

For the petition, David Smith said that in the “Pathways” trial: 

“Parents are being asked to consent to a potentially life-altering intervention to their children in the absence of a life-threatening condition, based on an unreliable diagnosis with an unknown trajectory.”

Rebecca Paul pointed out the flaws in the ethical committee process that had signed off the trial. Rosie Duffield spoke about the punishment meted out to whistleblowers who had expressed concern about the use of puberty blockers at GIDS over many years. 

Jonathan Hinder said: 

“Children of primary-school age cannot possibly give consent to these life-changing decisions. When they become adults, many of them will look back on what was done to them and ask, ‘How did this happen to me? How did the Government do this to me?’” 

Carla Lockhart, who said she had met Keira Bell, pointed out that minors are not allowed to drive, get married, buy alcohol or own a gun, and that for most puberty would naturally resolve gender dysphoria. Iqbal Mohamed quoted the statistics on this, saying: 

“They mean that the government are choosing to prioritise the interests of between five and 90 of the 226 children involved in the clinical trial at the expense of deliberately harming between 135 and 203 children, who will eventually come to terms with their birth sex.”

Joy Morrisey said the diagnosis is subjective, based on how the child feels, asking: 

“Can the long-term risk of medical intervention be justified by such a vague diagnosis?” 

Sarah Pochin said: 

“Last week, I hosted a roundtable about the indoctrination of our children in schools on this very subject, and I heard horrific stories from isolated parents whose children were lost to them because of brainwashing and the fantasy world they had been taught about at school.”

Jim Allister pointed out how the feelings of adolescents fluctuate, making them among the most vulnerable and in need of protection. 

Rebecca Smith drew on her experience as a “corporate parent” to flag the over-representation of looked-after children (those in the care of a local authority, living with foster parents or in residential homes) in the GIDS patient group, and pointed out that most of the girls were lesbians.

Gregory Stafford said: 

“When the evidence is weak, the risks are real and the patients are children, pressing ahead is not leadership, but recklessness.”

Six spoke against the petition and for the trial

The main defence of the trial was that Dr Cass had recommended one, with three MPs suggesting that pausing the trial was a political move, not justified by the evidence. They pointed out that this trial had gained ethical approval and that no new clinical information has emerged since the Cass Review. 

Carla Denyer and Dr Scott Arthur talked about meeting trans-identifying constituents or their parents, who expressed their regret that puberty blockers had not been available. Others talked cheerfully about “trans people”, with no acknowledgement of concerns about what “trans” means, how it might be determined in a child, or the historical evidence of desistance among most children claiming to be trans. 

Alex Sobel quoted a constituent who had told him: “To be a true ally you must support all trans people and their needs, not just adults.” He said that politicians should not meddle in medical decisions, then cited the World Professional Association for Transgender Health (WPATH) as “international best practice” and asked the minister for health “to meet advocacy groups such as TransActual”.

Two of these MPS said it was important to “do no harm” – and that making children wait for puberty blockers was harmful. To gasps of astonishment from the public gallery, Rachel Taylor, arguing that the trial must go ahead, said: 

“We cannot afford to sacrifice the future of vulnerable young people on the altar of ideology.” 

Heated exchanges about hounding and death threats 

Tonia Antoniazzi intervened while Emily Darlington was speaking to defend Professor Jacob George of the Medicines and Healthcare products Regulatory Agency (MHRA), whose input led to the trial being paused, saying he was a decent man who was being hounded. Darlington retorted: “A leader of a political party shouted ‘Traitor’ at me when I said we should watch our language around this issue.” She went on to say: 

“The honourable member for Canterbury (Rosie Duffield) has said she has received death threats; I get death threats too. This is not unique to the honourable member.”

Other MPs’ reactions to this indicated that they found it improbable that those opposing puberty blockers are issuing death threats.

Health spokespeople responded

The final three speakers were Helen Morgan, the Liberal Democrat spokesperson for health, followed by the shadow minister for health, Dr Caroline Johnson, who is a paediatrician, and finally Karin Smyth, minister of state for health (secondary care), to respond to all the points made. They all had more time to speak. 

The LibDem position was somewhere in the middle. Helen Morgan welcomed the pause to address the MHRA’s concerns but said the evidence was needed. She said that “treatment should first be based on talking therapies” and that waiting times are a concern: 

“All trans and non-binary people should be able to access the high-quality healthcare they deserve.” 

Dr Caroline Johnson for the Conservatives was less equivocal. She said: 

“To suggest persistent incongruence with gender stereotypes is wrong could undo years or decades of rolling back gender norms. If it is not causing the person any distress, why would we want to treat it, especially when we know that most children, even those with gender dysphoria who do have distress, will get better without any puberty blockers?”

She asked why there was a rush to do the trial rather than waiting for the data-linkage study, then had another pertinent question:

“What is the point of the treatment? It has been suggested that it helps transgender adults pass more easily as the opposite sex and potentially avoids surgical operations in adulthood, but how on earth can it be ethically, morally or medically right to treat a large group of children with risky medication to give cosmetic benefits to a much smaller number of adults?” 

She pointed out that this was not like prescribing potentially harmful drugs such as when chemotherapy being given to save a child’s life. Puberty blockers are to pause “a perfectly normal physiological process in a physically healthy child”, and she recapped on the known health risks such as bone density, cognitive development, fertility and sexual function, which others had mentioned earlier. She asked whether prescriptions of puberty-blocker alternatives had gone up since the ban (Karin Smyth said she would give an answer to this). She concluded: 

“I hope we can all agree that we do not need a clinical trial to know that helping a child to be at peace with themselves and their body is infinitely preferable to a lifetime of harmful medical intervention.”

Finally Karin Smyth, the minister for secondary care, talked through the background to the proposed trial and the Cass Review’s recommendations. She said that important final steps were being taken to enable the data-linkage study to begin and that the study analysis was expected to take around a year to complete. 

She pointed out the harms being done by private prescribers of puberty-blocking medication. She responded to the concerns about waiting times by saying that three new gender clinics have been opened since April 2024, when the Cass Review was published, and a fourth is about to open, all operating a model different from that of the now-closed GIDS clinic. 

She defended the planned clinical trial as “a key step that we are taking to build an evidence base to prove whether puberty blockers are safe and effective in treating gender incongruence and gender dysphoria”, but said nothing about the reasons for the pause or the next steps.

The ayes have it

At the end of the debate the chair asked for all those in favour (of the petition) to say “aye” and those against “no”. He then declared that “the ayes have it”, meaning that the majority of MPs in the room supported the petition to cancel the trial. 

What now?

That is the end of the process for the petition. But opposition to the puberty-blocker trial will continue. The legal challenge brought by James Esses and Keira Bell has been “stayed” – that is, paused – until the discussions between the MHRA and the trial’s sponsor, King’s College London, have concluded. It seems inevitable that the legal challenge will then resume, or a new legal case will be brought to oppose the new trial arrangements. 

Top right: Sex Matters director of campaigns Fiona McAnena with James Esses before the debate

The post MPs debate the puberty-blocker trial appeared first on Sex Matters.

A petition attracted nearly 150,000 signatures, securing a Westminster Hall debate, which is scheduled for 23rd March. On 10th March dozens of MPs heard about their constituents’ concerns in a lobby day organised by Women’s Rights Network, LGB Alliance and Sex Matters (pictured above). 

On 6th February detransitioner Keira Bell and therapist James Esses had applied for a judicial review. And on 20th February news broke that recruitment to the trial had been paused to give the research team at King’s College London time to respond to questions about serious physical risks to participants belatedly raised by the Medicines and Healthcare products Regulatory Agency (MHRA).

The latest development is another regulatory surprise: an immediate pause and proposed ban on NHS prescriptions of cross-sex hormones to under-18s announced on 9th March. At the moment, clinicians can prescribe cross-sex hormones from the age of 16. A 90-day public consultation is under way, due to close on 7th June. 

The announcement was accompanied by the publication of systematic reviews of the evidence for using combinations of puberty blockers and/or cross-sex hormones for various combinations of patient populations (male or female) and desired outcomes (“binary” transition – that is, identifying as the opposite sex – “non-binary” – identifying as neither sex).

It found no evidence supporting the standalone use of puberty blockers for minors who identify as non-binary, and none for cross-sex hormones in combination with puberty blockers for minors who identify as either non-binary or the opposite sex. For standalone use of cross-sex hormones for minors who identify as the opposite sex, it found only weak evidence. The results are a shocking acknowledgement that for over a decade the NHS has routinely offered life-changing hormone treatments to distressed minors without sufficient evidence to justify doing so. 

Delaying NHS treatment with cross-sex hormones from age 16 to age 18 further complicates any attempt to restart the puberty-blocker trial. Two of the concerns raised in the MHRA’s letter relate to the danger of being on puberty blockers for lengthy periods, and the harm blocking puberty does to children’s future fertility. The regulator suggested that these might be mitigated by setting a minimum age of 14 for participating in the trial, so that participants could be exposed to puberty blockers for a maximum of two years. (The current protocol merely requires children to have reached Tanner Stage 2, when pubertal changes start to become outwardly visible, usually around age 11 or 12.)

By limiting exposure to puberty blockers to a shorter period, the MHRA writes, the “potentially significant and, as yet, unquantified risk of long-term biological harms” will be lessened. One of these is early osteoporosis: puberty is a period when calcium is laid down in bones and blockers interrupt this process. But if the NHS does indeed raise the age for cross-sex hormones to 18, many trial participants are likely to be exposed to puberty blockers for four years, rather than at most two. 

As for infertility, puberty is when boys’ testicles become capable of producing viable sperm and girls’ ovaries become capable of producing viable eggs. Children who take puberty blockers are likely to grow up to have impaired fertility, especially if they proceed to cross-sex hormones, as almost all do. The idea is that by waiting till age 14, most participants in the trial will be physically mature enough that their ovaries or testes will be able to produce viable eggs or sperm, which can be collected and frozen. 

This suggestion is problematic on its own. For girls the procedure is unpleasant and invasive, and egg-freezing is still quite experimental. For both boys and girls it requires engaging with the biological reality of their sex, which is precisely what they are trying to flee from by entering the trial. Experience in gender clinics around the world suggest that when fertility preservation is offered, hardly any children take it up. 

More fundamentally, although the stated rationale for the puberty-blocker trial is to relieve children’s short-term distress, most participants are surely motivated by the desire to avoid sex-differentiated physical development. But a child who is mature enough to produce viable eggs or sperm will also have developed noticeable secondary sexual characteristics: there is no magical moment when fertility preservation is possible but the child still looks pre-pubescent.

These uncoordinated attempts to continue offering puberty blockers and cross-sex hormones despite no evidence of benefit and significant evidence of harm has brought the NHS to a point where its attempts at mitigation are mutually incompatible, especially when you consider why children want to go on blockers in the first place, which is to enable them to live “in stealth” – that is, with their true sex concealed from those around them. The most recent draft of official safeguarding guidance from the Department for Education, Keeping children safe in education (KCSIE), recognises that this is not possible for schools to accommodate safely and fairly.

Somehow, children are supposed to wait to start blockers until they are mature enough to produce viable eggs or sperm, remain on them for only a short period, not proceed to cross-sex hormones until they turn 18 – and simultaneously start blockers early enough that they don’t develop secondary sex characteristics. All this while they continue to be recognised and treated as their actual sex at school. 

Surely it’s time to acknowledge the central problem – that puberty blockers are not a treatment but a human-rights abuse – and to call the trial off.

The post Blocking puberty is a human-rights abuse – call off this drug trial now appeared first on Sex Matters.

• King’s College London Pathways documents
• Documents disclosed by the HRA with information on the “Pathways” trial 
• Judicial review claim
• Public consultation on the prescribing of masculinising and feminising hormones for children

The post Timeline of puberty blockers and cross-sex hormones for children  appeared first on Sex Matters.

Visit the CAN-SG website to find out more about its work.

The post Why the puberty-blocker trial was paused appeared first on Sex Matters.

Sex Matters has written to the MHRA and is organising a lobby day on Tuesday 10th March with the Women’s Rights Network and LGB Alliance. (Sign up at the WRN website.)

The decision to pause the trial came not long after Bayswater Support Group, Keira Bell and James Esses filed an application for judicial review against the Health Research Authority (HRA) and the MHRA challenging the lawfulness of their decision to approve the trial.

The key question the regulators were required to test before approving the study was whether the “foreseeable risks and inconveniences” of the drug trial for patients justified the “anticipated benefit” for individuals in the trial and other potential patients. 

There has been only partial disclosure of the minutes and papers of the decision-making process that led to the trial being approved. But what they reveal is a shambolic process in which the research ethics committee’s members and regulators failed to establish that there was any clear rationale for interfering with the natural pubertal development of healthy children before giving the study the green light.

The research ethics committee (REC) held only one full meeting, on 4th September 2025, and after that made decisions in a dwindling sub-committee. At the first meeting, the members accepted the assurance of the researchers that they “were confident that the risk/benefit balance was appropriate for the study” and that “there was no data at present on the cognitive impacts of puberty blockers”. 

The MHRA letter seems to accept that this confidence was misplaced. 

The legal challenge

The claimants – Bayswater Support Group, Bell and Esses – say that the claim that benefits outweigh risks was inaccurate and significantly misleading because there is data on the cognitive impact of puberty blockers from animal studies, and other established risks of harm of puberty blockers that were not considered. 

They also highlight that at some point last year the MHRA issued a written notice to the trial sponsors which set out 22 grounds for not approving the trial, including that the benefit of the treatment was not adequately identified. The Commission on Human Medicines (CHM) agreed with this and at a meeting on 18th September 2025 concluded that:

“On the evidence before them, the CHM had reason to think that on grounds relating to safety they might be unable to advise the grant of a Clinical Trial Authorisation for this trial at present.” 

But following further communications from the trial sponsors, the MHRA and CHM appear to have changed their minds. There has been no disclosure of how this happened.

The claimants highlight the many experts who raised concerns and were ignored. The Clinical Advisory Network on Sex and Gender (CAN-SG) engaged in extensive correspondence with both the HRA and the MHRA, and also wrote directly to the chair of the REC arguing that the anticipated benefits of the trial did not justify the risks, and highlighting the availability of alternative sources of data (the data-linkage study) and less harmful interventions that could be carried out. However, the HRA did not provide the REC with CAN-SG’s correspondence, on the basis that all these concerns would be covered in the application for ethical approval, and instead treated it as a “complaint”. The REC’s minutes show there was no consideration by committee members of the concerns raised by CAN-SG. 

Professor David Curtis, together with nine other clinicians and researchers with expertise in neuroendocrinology, psychiatry, psychology and medical ethics, also wrote to the HRA raising concerns – in particular about the effectiveness of a two-year follow-up period for the proposed trial and the risk of serious and irreversible harm. The HRA informed him that it had shared the letter with the chair of the REC who had decided there was no basis to share it with the rest of the REC. 

Does the trial balance risk and benefit?

In order to approve the trial the REC was required to consider whether the anticipated benefits justified its risks, and whether there was “some direct benefit” for the group of patients involved in the trial. The minutes show that they did not do this, but accepted the research team’s assurance that the risks and benefits would be assessed on a case-by-case basis by clinicians.

They also did not consider the broader risk entailed by putting children on a pathway to cross-sex hormones and social and medical transition. The desire to undergo this pathway of transition is one of the requirements of participants in the study. But instead of considering the full risk, the REC asked for “transition” to be taken out of the title of the study, and treated puberty blockers as a two-year intervention to improve a child’s mood and social functioning. 

The Participant Information Sheet for children says in answer to the question “What might be good about taking part?” 

“We do not know whether the treatment may help you…“ 

The trial is paused

On 11th February the MHRA wrote to the trial sponsors to raise concerns regarding the trial. On 23rd February Wes Streeting, the Secretary of State for Health and Social Care, told Parliament that the preliminary work to establish the planned “Pathways” puberty-blocker trial had been paused.

The judicial-review claim and the MHRA’s letter focus on the grave foreseeable physical risks and likely harms caused by puberty blockers on cognition, bone mineralisation and fertility. 

The MHRA letter correctly recognises that puberty blockers are the start of a medical pathway towards transition:

“It is likely that further GRHa treatment could be needed for many years (particularly if participants are significantly below the age of 16 at trial completion) as a bridging measure as cross-sex hormones are only prescribable from the age of 16.”

The idea of social transition remains unexamined

Any consideration of the risks and purported benefits of any part of this treatment pathway must assess whether the expected destination is realistic.

But the officials have not yet considered whether the fundamental promise being made to children that they can “live as the experienced gender” – and that it may be worth being sterilised and risking adult sexual function for this – is achievable. 

Medical transition has been promoted based on a widespread misunderstanding of the laws that protect everyone’s human rights. This was made absolutely clear by the Supreme Court’s judgement on 16th April 2025. 

We wrote to the Secretary of State for Health and Social Care last year, on 28th April and on 24th November, and on 16th February of this year, raising concerns about whether parents and children could meaningfully assent or consent to medical treatment based on hoped-for outcomes which simply cannot be achieved within the framework of UK law, and asking him to send the study back for further ethical consideration. 

The clarified interpretation of the Equality Act and the recognition that other people have human rights rules out the promise that a boy can grow up to be a woman or a girl can grow up to be a man. Individuals cannot expect to use opposite-sex services and spaces, or demand that other people treat them as if they were the opposite sex, whatever physical interventions they undergo.

On 13th February 2026 the High Court confirmed that the EHRC was correct to say that separate-sex facilities are lawfully provided on the basis of sex, not gender identity, and the Secretary of State for Education has published a new version of the statutory safeguarding guidance, Keeping Children Safe in Education, which confirmed that children cannot lawfully be permitted to use opposite-sex facilities at any time during their school career. 

The messages being presented to children and the promises being made to patients must be reassessed. Providing medical interventions with known physical and cognitive harms in pursuit of unachievable goals is unethical and likely to be unlawful. 

What now?

There will now be discussions between the MHRA and King’s College London to address the concerns raised in the MHRA letter.

Wes Streeting, the Secretary of State for Health and Social Care, will review the outcome of those discussions, taking clinical advice. He has said: 

“The clinical trial will not start to recruit until the issues the MHRA raised have been resolved. It will only be allowed to go ahead if the expert scientific and clinical evidence and advice conclude it is safe to do so.”

On Monday 9th March there will be a Westminster Hall debate on the puberty-blocker trial and on Tuesday 10th March there is a mass lobby of Parliament in Westminster. 

Now is the time to raise concerns with your MP about the trial, and to ask for a meeting and plan to come to the lobby day if you can. 

Sign up for the lobby day via the Women’s Rights Network, which will provide all the information you need. 

The post The puberty-blocker trial: paused but not yet stopped appeared first on Sex Matters.

The planned puberty-blockers trial has been paused, pending the review of concerns raised by one of the regulators, the Medicines and Healthcare products Regulatory Agency (MHRA). But it needs to be cancelled. Now is the time to tell your MP what this trial really means, and why there are much better ways to help distressed children. Blocking their puberty should never be an option.

More than 250 people have already signed up to join us for Lobby Day at Parliament on Tuesday 10th March 2026 to call on parliamentarians to Do No Harm and Stop the Puberty Blocker Trial. If you are one of those people, we look forward to seeing you.

The deadline has passed to sign up to get briefing notes and a template email. But anyone can turn up and ask to see their MP on the day. 

Organisers from Sex Matters, LGB Alliance and the Women’s Rights Network (WRN) will be there to support you with advice for your meeting, briefings about where to go and what to do, and materials to give your MP. You’ll need to make your way to the Houses of Parliament in Westminster for the afternoon of Tuesday 10th March. 

(This will take you to the WRN website for more information)

If you haven’t already, please write to your MP to request a meeting. You can find the template at the bottom of the page where you register for the lobby day. Copy action@womensrights.network into your correspondence and forward any replies you receive.

The post Lobby MPs to stop the puberty-blockers trial appeared first on Sex Matters.