The UK has paused a clinical trial on puberty blockers for young people after the medicines regulator raised safety concerns. The agency warned about unknown long-term biological risks and called for a minimum age of 14.
The Medicines and Healthcare products Regulatory Agency will discuss the issue with King’s College London next week. The Department of Health and Social Care confirmed that recruitment will not start until they resolve the concerns.
The Cass review prompted the trial. It found weak evidence for the benefits of puberty blockers in children with gender dysphoria. Dr Hilary Cass said a controlled study offered the only way to produce reliable answers.
The government said participant safety remains the main condition. Experts will review the evidence before any trial begins. The study will proceed only if it proves both necessary and safe.
King’s College London said the wellbeing of young people and their families guides the project. Researchers will continue working with the regulator. They aim to build a stronger evidence base for future care.
The original plan allowed children as young as ten to join. The regulator now wants a stepwise approach that starts at age 14 because of uncertain risks.
NHS England has already ended the routine use of puberty blockers for minors and limited them to research.
Professor Sir Jonathan Montgomery said the regulator seeks to improve the study design, not cancel it. He described the pause as a proper safety measure.
