The National Health Service (NHS) has announced funding for a £10.7 million clinical trial investigating the use of puberty blockers in young people with gender dysphoria, despite the UK government's current ban on their routine prescription to under-18s.
The research, led by King's College London, follows recommendations from Baroness Hilary Cass's landmark review into gender identity services, which identified significant gaps in evidence regarding the medications' benefits and risks.
Trial Design and Objectives
The NHS-funded study will monitor young people who, with parental consent, receive puberty suppressing hormones over a two-year period. Researchers will track participants' physical, social, and emotional wellbeing to determine potential benefits. The trial will also include a control group of children attending NHS gender clinics who do not receive puberty blockers.
"This suite of research will examine the evidence for a range of clinical care, including the use of puberty suppressing hormones, following advice from the Cass Review," said Professor James Palmer, NHS national medical director for specialised services.
The trial will be conducted at new NHS gender dysphoria services in London, Bristol, and Liverpool, with potential expansion to three additional centers. All research will be subject to strict ethical and regulatory approval processes.
Scientific Context and Medical Background
Puberty blockers, formally known as gonadotropin-releasing hormone (GnRH) analogues, work by suppressing sex hormones such as testosterone and estrogen. Originally developed to treat precocious puberty in children under eight, they were adapted for gender dysphoria treatment in the UK in 2011, based on the "Dutch protocol."
The medications temporarily halt physical development, preventing voice deepening and facial hair growth in natal males, and stopping breast development and menstruation in natal females. Proponents have argued they provide a "pause" for young people to consider their gender identity without the distress of unwanted physical changes.
However, the Cass review found limited evidence that these drugs effectively reduce psychological distress associated with gender dysphoria. A Tavistock clinic study of 44 children given puberty blockers between 2011 and 2014 showed no statistically significant improvement in psychological wellbeing, with some participants experiencing increased distress.
Medical Opinion Remains Divided
The medical community remains sharply divided on the issue. Baroness Cass maintains that a clinical trial is essential precisely because of the polarized views and lack of robust evidence.
"There are very strongly held but polarised views on the use of these medications, with some people thinking they should be stopped entirely for young people with gender dysphoria, and others arguing they should be much more freely available," Cass stated in her first public comments since the trial announcement.
"Both these positions have some cogent arguments, but the two positions are incompatible. From a clinical research perspective, this is called equipoise. We do need further research to fill some of the evidence gaps, to remove uncertainty for the young people, their families and clinicians," she added.
Dr. Hannah Ryan, a specialist registrar in clinical pharmacology at Royal Liverpool University Hospital and member of the Clinical Advisory Network on Sex and Gender (CAN-SG), expressed skepticism about the trial's feasibility.
"We have no way of predicting which children will persist with gender dysphoria into adulthood and who will simply desist," Ryan said. "Historically, around three quarters will desist without any intervention at all. You could not design inclusion criteria for a trial that would exclude those kids who will just simply grow out of this and not become transgender adults."
Regulatory Context and Controversy
The trial announcement comes against a backdrop of significant regulatory changes. In December 2023, the UK government implemented an "indefinite ban" on prescribing puberty blockers to under-18s, which will remain in place until at least 2027.
This policy shift followed the closure of the controversial Gender Identity Development Service (GIDS) at the Tavistock Centre in north London, which had been criticized for its approach to prescribing these medications.
The political environment surrounding the issue remains contentious. The government has already defended against one judicial review challenging the puberty blockers ban, brought by TransActual UK and the Good Law Project. Now, a group led by "detransitioned" patient Keira Bell and psychotherapist James Esses has threatened legal action against the Health Research Authority if it approves the Pathways trial.
Long-term Concerns and Research Gaps
Some medical experts argue that before initiating new trials, researchers should first analyze outcomes from the approximately 2,000 children previously treated with puberty blockers at the Tavistock clinic. However, accessing these medical records has proven challenging.
Professor Sallie Baxendale of University College London raised concerns about potential long-term neurological impacts: "We currently don't know what the long-term effects of [interrupting puberty] will be, or whether the brain ever catches up on that period of suspended development. A clinical trial looking at the impacts in the short term won't give us these answers."
Conversely, Professor Dominic Wilkinson, a paediatrician and medical ethicist at Oxford University, supports the trial approach: "When there is genuine uncertainty, the way to address it is by doing carefully designed and conducted trials. We need to tackle it head-on."
As the NHS continues to expand and improve services for children and young people with gender dysphoria, this research represents a significant step toward establishing an evidence base in an area characterized by intense debate and limited scientific consensus.
