Puberty Blockers Clinical Trial

Jamie Stone Excerpts

Monday 23rd March 2026 Westminster Hall

[Jamie Stone (Caithness, Sutherland and Easter Ross) (LD)]

I beg to move,

That this House has considered e-petition 751839 relating to the clinical trial into puberty blockers.

It is always a pleasure to speak under your chairmanship, Mr Mundell. I sincerely thank everyone I met in preparation for this debate: the legal and medical professionals who shared their expertise and the individuals with deeply personal, lived experience on both sides of this discussion. It goes without saying that this is a complex topic. I am grateful for the time and care that people have taken to help inform this debate.

I also thank the petition’s creator, James Esses, and petition supporter and campaigner Keira Bell. I had the pleasure of meeting them ahead of this debate, and they are watching today. Their petition asks that the clinical trial for the use of puberty blockers be cancelled. They believe that medical intervention in this area is dangerous, poorly evidenced and ethically questionable. They have asked Parliament to ensure that children are protected from potential harm.

I want to make it crystal clear that this debate is not about trans rights or whether people who identify as transgender have the right to exist and live free from discrimination. This discussion focuses on a clinical and ethical issue: whether puberty blockers should be prescribed to children experiencing gender dysphoria, and specifically whether a new NHS-backed clinical trial into their use should proceed.

Puberty blockers are medicines that suppress the production of sex hormones. They press pause on puberty, delaying changes like periods, breast development, voice changes and facial hair growth. Historically, they have been prescribed to children who enter puberty unusually early and, in some cases, for the treatment of cancers or endometriosis. Importantly, they are distinct from gender affirmation or cross-sex hormones. Blockers temporarily pause development, while cross-sex hormones actively induce the physical changes of the opposite sex and are generally irreversible.

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.

[Tonia Antoniazzi (Gower) (Lab)]

The hon. Gentleman is making a very good start to his speech. I appreciate that this is very contentious, but I am concerned about the manner in which young people—children—are asked questions. The KIDSCREEN-10 index is a primary outcome measure for the PATHWAYS trial, and when I look at the questions, I wonder how my son would have answered them aged 11. One of them asks:

“Have your parent(s) treated you fairly?”

The truth is that any child at that age would probably say, “No.” Does the hon. Gentleman share my concern that these questions are not fit for purpose?

[Jamie Stone]

I thank the hon. Member for her intervention, but she will understand that it is my job as Chairman of the Petitions Committee to present a fair description of both sides of the discussion, which is what I hope to do.

James Esses, who started the petition, is a psychotherapist, and he impressed on me the benefit that good psychiatric intervention could have, without medicalisation. Puberty, he argued, is rarely a picnic for anyone—it can be confusing, uncomfortable, and sometimes miserable—but it is an essential developmental stage, and suppressing it pharmacologically could alter physical and cognitive development in ways we do not yet fully grasp. His argument is not to remove care for children experiencing gender incongruence, but to focus efforts on careful psychological support.

Others question the trial’s purpose, noting that puberty blockers have already been paused for new NHS patients with gender incongruence, following concerns about safety. They fear that authorising a new trial implies a level of confidence that the evidence base does not yet justify, arguing that enough data exists to recognise the potential harms, from reduced bone density to uncertain impact on brain development. Continuing could erode the safeguards that protect young people.

[Graham Stringer (Blackley and Middleton South) (Lab)]

The hon. Member is making great efforts to be balanced in his presentation on behalf of the Petitions Committee. He says this is a complex area, but surely 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.

[Jamie Stone]

I note the sincerity with which the hon. Gentleman makes his remarks. There is the legal and ethical question of whether a child can ever truly consent to something like this.

[Stuart Anderson (South Shropshire) (Con)]

I have five children, and have watched half of them go through puberty. They continually change their minds about things. Ethically, I can see no justification for allowing children to be experimented on. What might be a short-term solution could become a permanent solution that people often grow to regret.

[Jamie Stone]

I thank the hon. Member for his intervention, which was, I believe, made with as much sincerity as the previous intervention.

[Sir Julian Lewis (New Forest East) (Con)]

I believe many children were treated with puberty blockers, among other drugs, before the Gender Identity Development Service programme was closed down. Does the hon. Member know what has happened to all the data from those children who were previously treated, or why it should be necessary to treat any more children with these drugs until enough time has elapsed to enable that data, and the treatment’s consequences, to be verified?

--- Later in debate ---

[Jamie Stone]

What I am about to say relates to the right hon. Member’s intervention. It is not unusual in medicine for children to participate in clinical trials, provided that there are robust safeguards, clear parental consent and proper oversight. But can a distressed teenager and a family desperate to help truly grasp these long-term implications? The legal experts I consulted spoke about the delicate ethics at play. Medical research always involves balancing competing risks: the risks of harm from an intervention versus the risks of harm from withholding it.

Puberty blocker trials pose unusual challenges as they cannot include placebos, so the design requires special scrutiny to ensure that informed consent is meaningful. There is still work to do to ensure that children and parents fully understand what entering a study means. On the other hand, opponents of the petition—those who support the new trial—say that the only way to reach clear conclusions about safety and efficacy is through rigorous, carefully monitored research. We do not yet know about the potential harms of puberty blockers for treating gender dysphoria, but we do know that the effects of cross-sex hormones can be irreversible.

Following the Cass review, NHS England proposed a very different approach from the old Tavistock model, focusing on smaller numbers and much stricter controls. The new design would have national oversight, tight eligibility criteria and a multidisciplinary team around each young person, and only about 5% of participants might receive puberty blockers compared with around 27% who were prescribed them while at Tavistock.

Also important is that cancelling the NHS trial would not prevent young people from accessing puberty blockers. In some gender clinics, clinicians report that between 10% and 20% of clients are obtaining them privately or online, outside regulated healthcare systems. Those unmonitored routes carry greater risks because dosages, purity and outcomes are not tracked or supported. Proponents of the trial point out that without direct research we remain in a state of uncertainty, which carries its own risks. If puberty blockers help some young people to avoid serious distress, we need to understand that better.

If the evidence ultimately shows that the risks outweigh the benefits, that too must be established through high-quality data. Without such evidence, none of us—doctors, parents or policymakers—can make sound judgments. Of course, participation in any trial is voluntary. Families will continue to have the right to decline. The aim of the study is not to push young people towards any one outcome, but to understand what support is appropriate for different individuals.

I want to end my speech by returning to the people at the heart of this issue. I have spoken to individuals who feel deeply harmed by medical intervention, such as Keira Bell, whose story has been widely discussed. Her experience matters, as do the experiences of all those who regret the care they have received. I have also had the pleasure to speak with Maxine Heron, whose experience with puberty blockers was profoundly positive. Having the option to pause puberty spared her immense distress, and she has experienced no negative health outcomes. 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.

We must hold both kinds of stories with equal seriousness. Regret exists, but so does gratitude. The aim of research is not to erase one side of the story, but to understand why experiences differ, and crucially, how best to help every child who is struggling. Without doubt, this is one of the most challenging questions before us: how to protect young people, respect autonomy and uphold scientific integrity. I, for one, do not pretend that it is easy.

I hope today’s debate will help to address some of the challenges, and reassure those who have signed the petition that their concerns are being taken seriously. I can see with my own eyes that many colleagues wish to contribute. I will therefore draw my remarks to a close. I look forward to the contributions to this debate, especially the reply from the Government, which I believe will be instructive.

[Several hon. Members]

rose—

--- Later in debate ---

[Jamie Stone]

I trust that this evening’s debate has given a flavour of what life on the Petitions Committee is like—it brings its challenges and informative debate. I want to thank all those who have spoken; they have done so with sincerity. Opinions differ, but there is no doubt that hon. Members feel very strongly about the issue. I also thank those in the Public Gallery. At the end of the day, the work of the Petitions Committee is about ensuring that an issue is properly aired in this place and that petitioners are heard. I believe that has been done tonight, and I thank everyone.

Question put and agreed to.

Resolved,

That this House has considered e-petition 751839 relating to the clinical trial into puberty blockers.