We genuinely don't know if there are harms
In the long and unresolved struggle to understand how medicine should meet the needs of gender-questioning young people, a clinical trial in the United Kingdom now stands as both a proposed answer and a new battleground. Dr Hilary Cass, the physician who reviewed NHS gender services, argues that without rigorous evidence gathered under careful oversight, children will not be protected — they will simply be pushed toward unregulated harm. The trial, set to begin recruiting in August 2026, seeks to do what years of political and ideological contest have failed to accomplish: let science speak where certainty has not yet been earned.
- Dr Cass warns with unusual directness that blocking the trial will cause more harm to children than running it, pointing to eleven-year-olds already accessing testosterone through unregulated channels.
- A 2024 government ban on puberty blockers for under-18s, intended as a safeguard, may have inadvertently driven vulnerable young people toward unsupervised and irreversible interventions.
- Legal challenges from parent groups and campaigners allege the trial is unethical and that children cannot meaningfully consent to treatments with potential fertility consequences — threatening to delay recruitment before it begins.
- Researchers have negotiated minimum age thresholds and built in close monitoring of bone density, brain function, and fertility, framing the trial as the only responsible path through an evidence vacuum.
- The Conservative Party's push for a parliamentary vote risks converting a clinical question into a political one, while trans advocacy groups argue the ban itself should be lifted entirely.
Dr Hilary Cass has staked her professional credibility on a single conviction: that preventing a clinical trial on puberty blockers will harm more children than conducting one. Speaking to the BBC without qualification, she described a landscape in which the 2024 NHS ban on puberty-blocking drugs has not protected young people so much as redirected them — toward unregulated sources, toward irreversible hormones accessed without oversight. She cited children arriving at clinics already on testosterone at age eleven, a development she believes a puberty blocker might have forestalled by creating space for therapy and reflection.
The trial, announced in late 2025 and stalled briefly by regulatory negotiations over age thresholds, is now set to begin recruiting in August. Participants will be monitored closely for effects on bone density, brain function, fertility, and overall wellbeing, with the drugs halted if concerns arise. Health Secretary James Murray acknowledged his own discomfort with the situation but argued that grounding future policy in clinical evidence was the only responsible course.
Opposition is fierce. The Bayswater Support Group, representing parents skeptical of medical approaches to gender questioning, has filed legal action alleging the trial is unethical and that children cannot give meaningful consent to interventions that may affect their fertility. Cass counters that the uncertainty about harm is precisely the reason the trial must happen — the evidence simply does not exist yet. Meanwhile, trans advocacy groups welcome the research but argue the ban itself should be reversed, and the Conservative Party has called for a parliamentary vote, threatening to transform a clinical matter into a political one. Whether the courts will permit the trial to proceed as planned remains an open question.
Dr Hilary Cass has staked her credibility on a conviction: that blocking a clinical trial on puberty blockers will cause more damage to young people than running one. She is not hedging. "I am absolutely convinced that more children will be harmed if we don't do the trial than if we do," she told the BBC, her language stripped of qualification.
The trial itself is straightforward in design but freighted with controversy. Researchers will give puberty-delaying drugs to gender-questioning children under close observation, measuring the impact on bone density, brain function, fertility, and overall wellbeing. The NHS banned these drugs for under-18s in 2024—a sweeping, indefinite prohibition on both private and public prescriptions. Cass argues the ban created a vacuum. Without legal access, she contends, young people are turning to unregulated sources. She cited a stark example: children arriving at clinics already on testosterone at age eleven, a masculinising hormone that produces irreversible changes and should not be prescribed to anyone under sixteen in the UK for gender care. A puberty blocker, in her view, might have bought time—space for therapy, for thought, for a different path.
The trial was announced in November but stalled in February when medical regulators proposed age restrictions. After negotiation, researchers settled on eleven as the minimum for birth-registered female participants and twelve for birth-registered males. Recruitment is scheduled to begin in August, though legal action threatens to delay or derail it entirely. Campaigners have filed suit, arguing the trial is unethical and that children cannot meaningfully consent to an intervention that could damage their fertility. Bayswater Support Group, which represents parents skeptical of medical approaches to gender questioning, claims the trial will cause irreversible harm and will not answer the fundamental questions about whether these drugs are safe or effective.
Cass pushes back on what she calls exaggerated claims about risk. "We genuinely don't know if there are harms," she said—a statement that cuts to the heart of the impasse. The trial, she insists, is essential precisely because the evidence does not exist. Young people will be monitored closely, and the drugs will be stopped if concerns emerge. Health Secretary James Murray echoed this logic in Parliament, saying he felt "uncomfortable and uneasy" about the matter but believed basing future policy on clinical evidence was the only responsible path forward. He emphasized the safeguards in place.
But the political ground is unstable. The Conservative Party has signaled it wants a House of Commons vote, turning a clinical question into a parliamentary one. TransActual, a campaign group for trans people, welcomed the trial but called on the government to reverse the ban entirely and provide care based on informed consent rather than what they termed "the latest moral panic." Cass frames this as a matter for science and clinical judgment, not politics or ideology. She argues that young people and their families have been failed by NHS services for too long. The trial, in her view, is the only honest way forward—a way to gather the evidence that does not exist, to answer questions that cannot be answered without it, and to do so under conditions of genuine safety and oversight. Whether the courts will allow it to proceed remains uncertain.
Citações Notáveis
More children will be harmed if we don't do the trial than if we do— Dr Hilary Cass
Following clinical advice and basing future decisions on clinical evidence is the right way to move forward— Health Secretary James Murray
A Conversa do Hearth Outra perspectiva sobre a história
Why does Cass believe the trial is more protective than the ban itself?
Because the ban created a vacuum. Without legal access, young people seek unregulated sources—testosterone from unknown suppliers, dosages without medical oversight. A trial at least puts them in a clinic, monitored, with the option to stop if harm emerges.
But the campaigners say children can't truly consent to something that might damage their fertility. Isn't that a real problem?
It is. That's why it's a legal question now, not just a clinical one. Cass would say the alternative—no evidence, no trial, young people on unregulated drugs—is worse. But "worse" is a judgment call.
What does Cass mean when she says "we genuinely don't know if there are harms"?
That the evidence simply doesn't exist. The drugs have been used, but not studied rigorously in this population. So claims about harm are speculative. A trial would either confirm those fears or dispel them.
Is this really a clinical question, or has it become political?
Both. Cass wants it to be clinical. But the Conservative Party wants a parliamentary vote. TransActual wants the ban reversed. Everyone is using the language of evidence and safety, but they're arguing about values underneath.
What happens if the legal challenge succeeds?
The trial doesn't start in August. Young people remain in the gap—no legal access, no clinical oversight, no evidence being gathered. The impasse continues.