Puberty Blockers Clinical Trial

Iqbal Mohamed Excerpts

Monday 23rd March 2026 Westminster Hall

[Iqbal Mohamed (Dewsbury and Batley) (Ind)]

It is a pleasure to serve under your chairship, Mr Mundell. This is a Government who have shown that they care for the safety and welfare of children. They supported the Online Safety Act 2023 to counteract harmful digital content and removed, albeit eventually, the punitive two-child benefit cap to reduce poverty. The Government have committed to halving violence against women and girls, and have banned the pre-watershed advertising of junk food on TV.

However, the trial flies in the face of the Government’s explicit mission to protect children from harm. It would expose children to severe and irreversible harm when viable, less harmful alternatives are available. Despite that, the Government are happy to permit a clinical trial that would give puberty blockers to 226 children. Research has shown that over 95% of children who start out on puberty blockers continue on to cross-sex hormones, while other research has shown that between 60% and 98% of children with gender dysphoria will outgrow that feeling and go on to live a normal, natural, healthy life in their born body.

[Rachel Taylor]

Will the hon. Gentleman give way?

[Iqbal Mohamed]

I am going to continue, given the lack of time.

The numbers are important. 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. I ask the Minister, will the Government now confirm that the current pause—which I welcome and am grateful to the Government for—will remain in place unless and until all safety, ethical and scientific concerns are fully and transparently resolved?

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[Dr Caroline Johnson (Sleaford and North Hykeham) (Con)]

It is a pleasure to serve under your chairmanship this afternoon, Mr Mundell. I must first declare an interest as an NHS consultant paediatrician. I thank James Esses for the petition and the thousands of people who have signed it, including many of my constituents, for enabling today’s important debate. I also thank the hon. Member for Caithness, Sutherland and Easter Ross (Jamie Stone) for leading the debate so well.

The petition asks the Government to cancel the puberty blockers trial and to safeguard vulnerable children. Perhaps it is worth considering whether clinical trials in children are a good idea in principle. The answer, of course, is yes. Children are not just small adults; they have different illnesses from adults, they present with different symptoms and respond differently to medication, and they require different doses at different ages. Properly designed clinical trials ensure that children’s medicines are safe and effective for them.

However, today we are discussing one particular trial: a proposal to give puberty blockers—gonadotrophin-releasing hormone analogues—to children, specifically for gender incongruence. Perhaps at this point it is worth considering why doctors and others prescribe medication; we do it to treat or cure disease, to treat or lessen symptoms and to aid in diagnosis.

What does this trial seek to do? On the face of it, it seeks to establish whether puberty blockers are a safe and effective treatment for gender incongruence. ICD-11 defines gender incongruence as:

“A marked and persistent incongruence between an individual’s experienced gender and the assigned sex”.

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?

Currently, there is no way to identify which children will persist with a trans identity as adults and which will not. The much-delayed data linkage study could help with that. It could enable more targeted interventions and may also provide information on the long-term outcomes for people who have taken puberty blockers in the past. However, the Government insist on pushing on with the puberty blockers trial anyway, before the data linkage study is complete. Why? In written parliamentary questions, Ministers have said that they expect the data linkage study to be finished by April 2027, so what is the rush?

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?

There are also cosmetic risks to the treatment. The penis grows very little between the ages of three and 10 years. The use of puberty blockers restricts growth, meaning those with a persistent trans identity may struggle with having enough tissue for a vaginoplasty surgery, and those who do not have a persistent trans identity may struggle with normal intimate relationships.

As mentioned earlier, the Secretary of State has said that he has confidence in this trial. Now it has been paused, we can presume that he is not quite so sure. But can we, patients and the general public have confidence in this trial? There are certainly causes for concern. In fact, there are so many that I cannot speak of them all today, but I would like to speak of a few in the time I have available.

First, on the selection of patients, we have had a dramatic change in the demographic. There has always been a small number of children uncomfortable in their own bodies, but there has been a rapid increase, which is not fully understood, particularly among girls. Many of them are in care, some have autism spectrum disorders and many are same-sex attracted. We need to understand this before prescribing irreversible treatments.

We do prescribe—and I have prescribed—drugs that are high risk or potentially harmful to children. An easy example would be chemotherapy, but that is being given to save a child’s life; it is not used to pause a perfectly normal physiological process in a physically healthy child. The risks of these treatments have been listed today, but I will list just a few: fertility problems; idiopathic intracranial hypertension; demineralisation of bone density, leading to fractures; in some studies, an increase in depression and anxiety; and the long-term loss of sexual function in some patients. We have discussed consent. How do you get consent from a parent of a child—a boy or a girl at Tanner stage 2—about long-term sexual function and fertility?

On the design of the trial, it is said to be a randomised controlled trial. Well, it is, but that is a bit of a fudge, because instead of an actual randomised controlled trial where some patients receive puberty blockers and some do not, it has given some now and some slightly later, with a very short difference in the timing. The comparison group that does not have any puberty blockers at all is taken from a slightly different population, which introduces an unnecessary bias. The trial’s organisers have said that they are doing that because they think the children would get the drugs from elsewhere or from abroad, but that is not how we do medical trials. When I have raised this issue, Ministers have responded that it cannot be blinded, but blinding and randomisation are not the same thing. The trial is also far too short to provide data on long-term outcomes.

On the process of the trial, the hon. Member for Gower (Tonia Antoniazzi) raised questions about what children are being asked as part of this trial. Why is the trial proposing to ask children about their sexual experiences? Why is this helpful to the trial?

[Iqbal Mohamed]

Will the hon. Member give way?

[Dr Johnson]

I will not because I am aware of the time.

The Commission on Human Medicines’ report heard that, because trials of puberty blockers have been blocked, some clinicians are trying to use other drugs to limit puberty, such as spironolactone and cyproterone acetate. There have been reports that the number of prescriptions for spironolactone in 10 to 17-year-olds is going up. Could the Minister confirm whether that is the case and what the Government are doing to look into it?

The MHRA was happy with the process; now it is not. What has changed? None of the issues raised seem to have not been raised before. The Government are being secretive about it: in February, Ministers brought forward a written statement referencing an MHRA letter in November, but the Minister is refusing to publish it. I have asked Ministers whether they talked to MHRA officials about the trial before February 2026, and they will not answer the question. There was a letter between the MHRA and KCL; I asked when it was received, when the Department became aware of it and when Ministers became aware of its contents. They will not tell me.

What about the people controlling the trial? As has also been mentioned during this debate, Professor Jacob George has been recused from further involvement. According to the MHRA’s statement, this is “a precaution”, because of social media posts made before his involvement. Why have those who have made the opposite type of comment not been recused too? This will inevitably make members of the public think there is bias involved.

There is an oversight board. What has the Minister done to ensure that the clinicians and scientists on that board are impartial, and that it is balanced between both perspectives? The Tavistock trial was supposed to report to the MHRA, but it did not, seemingly with no consequence. There will be lay members on the board with lived experience; will one of those be a detransitioner, or will they all be people on one side? That would increase the perception of bias in this trial.

In summary, this is a trial of risky medication on healthy children, most of whose features of gender incongruence will resolve in time, given normal puberty. What is particularly worrying is that, at the end of this treatment, the trial has so many flaws that it is bound to be disputed, whatever the result.

To give this treatment, the lead clinician will need to think that there is a reasonable prospect of a patient benefiting from puberty blockers. Given all that has been said, how can any clinician believe that that is the case? 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.

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[Karin Smyth]

I am not going to give way; I am going to get through these points.

The safety and wellbeing of children and young people have always been the driving consideration in every decision we have made regarding this trial, and always will be. That is why the trial sponsor has paused recruiting until these issues can be resolved. There have been calls today to cancel the pause, to continue with the pause and to cancel the trial, but the position is that the trial is paused until the issues are resolved, because we will not compromise an inch on safety. The trial will proceed only if the regulatory approval is reconfirmed. We will provide an update on the outcome of those discussions as soon as we can.

[Iqbal Mohamed]

Will the Minister give way?

[David Mundell (in the Chair)]

Order. I think the Minister has made it clear that she is not taking interventions.