Puberty Blockers Clinical Trial

Tonia Antoniazzi 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.

--- Later in debate ---

[Josh Newbury (Cannock Chase) (Lab)]

It is a pleasure to see you in the Chair, Mr Mundell. At the outset, I want to acknowledge the strength of feeling on all sides of this debate, and our responsibility in this House to provide clarity that is grounded in evidence and centred on the wellbeing of the young people we are talking about.

The petition calls for the cancellation of the planned clinical trial of puberty-suppressing hormones, describing them as unsafe and inconsistent with safeguarding. However, the reality is that Dr Cass was clear in her review that we are lacking evidence, and that one of the scenarios where she believed that puberty blockers should be prescribed for gender incongruence is a clinical trial. A trial is a response to uncertainty, focused on ensuring that clinical decisions are made on a foundation of robust evidence.

I find it a little more than ironic that, when the Cass review was published, many of the voices now telling us that a trial should not go ahead were saying that the Cass review should be accepted and implemented in full. They have gone from saying, “We need the evidence,” to, “This trial should be stopped.” If someone can show me another way of properly gathering clinical evidence other than a full clinical trial, then I am all ears, but, in reality, we are talking about shutting down options for trans people. With waiting times for a first appointment for a gender identity service currently standing, in many cases, at more than five years, it is not as if there are copious alternatives out there for this group of young people. Many are waiting the entirety of their adolescence just to start treatment. Would we tolerate that for any other group of patients? I doubt it.

[Tonia Antoniazzi]

Will my hon. Friend give way?

[Josh Newbury]

In the interest of time, I will not.

Although I respect the concerns that have led many to sign the petition, I urge colleagues to reflect on the consequences of the course of action it proposes. Cancelling research does not resolve uncertainty, but entrenches it. In doing so, it risks leaving vulnerable young people without the evidence base needed to support safe, informed and compassionate care. As someone who is proud to be an ally of the trans community, I believe that we have a duty to ensure that trans young people hear a clear message from this House: they are supported, respected, cared for and never alone.

--- Later in debate ---

[Tom Tugendhat (Tonbridge) (Con)]

It is a pleasure to serve under your chairship, Mr Mundell. We should start off by recognising that the life choices that adults make, in whatever way they make them, are to be respected and not criticised. This matter is not in any way a criticism of anybody who chooses a trans identity or who identifies as trans, or who chooses any other identify or identifies in any other way. It is simply about the experimentation on children.

Let us be clear: we would not tolerate any form of medical experimentation on children in such an uncertain category with any other treatment. We would, quite rightly, put forward the Hippocratic oath to do no harm. To change that, particularly for a group of children who are often already suffering from some other element of potential harm, including autism, as the hon. Member for Canterbury (Rosie Duffield) mentioned, would be to re-victimise children who are already vulnerable. This issue must be treated delicately and carefully, but the truth is that it is getting wrapped up in identity politics and being played with politically by those who wish to advertise their progressive credentials but who are forgetting that it is fundamentally about one thing: the protection of children.

[Tonia Antoniazzi]

Will the right hon. Gentleman give way?

[Tom Tugendhat]

I will not. Whatever the views of people in this room, there is a second element that this Government must consider. We are already seeing honourable individuals like Keira Bell who have raised the problem of detransitioning, and we are seeing the legal costs of their actions against the state. What money has the Government set aside for legal action for those who are too young to consent because they are not 18 years old and who will therefore able to bring legal action against the state for any experimentation that was done on them, as would have happened in this circumstance?

[Emily Darlington (Milton Keynes Central) (Lab)]

It is a pleasure to serve under your chairmanship, Mr Mundell. I want to start with the expression, “Do no harm.” To be clear for the people who have come to speak to me—parents and young people themselves—we are doing them harm by not giving them the treatment they need, with the wait times of six years, and potentially in respect of puberty blockers, where that is agreed with their healthcare professionals.

My overarching concern is that the clinical trial was suggested in the Cass review. It was proposed and designed in conjunction with the MHRA, but then the MHRA changed its mind. Why was that? Dr Hilary Cass said:

“There are no new research findings and the MHRA hasn’t presented any new evidence. It feels to me like they are responding to political pressure rather than to science.”

That is what she said; I was quoting her verbatim. It was her review that the people around this Chamber wanted us to listen to and to make changes in response to, so we have to listen to her in this instance as well.

The MHRA should operate without any political interference or fear of legal action, yet the MHRA itself referenced potential legal action in relation to the trial as one of the reasons why it changed its mind. That is a problem. The MHRA is there to make sure that anything from clinical trials to medical technologies and new drugs are dealt with on the basis of science and science alone.

[Tonia Antoniazzi]

The problem is that the MHRA lead, Professor George, is being hounded and scapegoated after recusing himself. It is really sad to see a professional in such a situation. I urge my hon. Friend to use words with caution, because he recused himself. He is a great man who is being hounded.

[Emily Darlington]

I am not for hounding any particular individual. The only person I have referred to by name is Hilary Cass and she has been on the public record. I have been hounded for my views as well—

[Tonia Antoniazzi]

We all have.

[Emily Darlington]

Exactly, and that is completely inappropriate. A leader of a political party shouted “Traitor” at me when I said we should watch our language around this issue. I do not know who they think I am a traitor to, but I am certainly not one to the human race. The hon. Member for Canterbury (Rosie Duffield) has said she has received death threats; I get death threats too. This is not unique to the hon. Member.

The MHRA should not be in an environment where it has any fear of any legal action; it should only look at the science. Many in the community feel that the trial has now become too political for anybody to touch and that we have forgotten about those children who, quite frankly, if we do not do anything for them, we are doing harm.

--- Later in debate ---

[Rachel Taylor]

For the sake of time, I will not.

The need to be guided by evidence is precisely why the current situation is so troubling. It is concerning that the MHRA initially raised no objections to the trial when it was approved but has since changed that position. As Dr Cass made clear, no new evidence has been presented to justify that shift. That raises serious questions about the basis of the decision, and whether an independent regulator has buckled to pressure from a well-funded lobbying campaign. As a consequence, vital research is now at risk, and that matters. The trials are not an optional extra; they are the mechanism through which we build the evidence base that critics say is lacking.

[Tonia Antoniazzi]

Will my hon. Friend give way?

[Rachel Taylor]

No, I am not giving way.

We cannot afford to sacrifice the future of vulnerable young people on the altar of ideology. The trials received ethical approval and were recommended by one of the country’s foremost experts in child health. It is vital that they go ahead so that we can build the evidence we need to support safe, effective healthcare for young trans people.