The UK has suspended a clinical trial on puberty blockers for young people after the medicines regulator raised safety concerns. Officials warned about unknown long-term biological risks and called for a minimum age of 14.
The Medicines and Healthcare products Regulatory Agency will meet King’s College London next week. They will review the protocol and address wellbeing issues. The Department of Health and Social Care confirmed that recruitment will not start until they resolve these points.
The Cass review had recommended the trial. It found weak evidence for the benefits of puberty blockers in children with gender dysphoria. Dr Hilary Cass said only a controlled study could clarify the treatment’s effects.
Government officials said safety remains the clear priority. Clinicians will examine the evidence before any approval. The trial will proceed only if experts judge it safe and necessary.
King’s College London said it will continue working with the regulator. The university stressed that the study follows strict scientific standards and aims to improve future clinical decisions.
Researchers had planned to recruit 226 participants over three years. The original design allowed children as young as ten. The regulator has now urged a step-by-step approach that begins at age 14 because of uncertain biological risks.
NHS England had already ended routine use of puberty blockers for minors and limited them to research settings. Legal expert Sir Jonathan Montgomery said the pause strengthens the study design and shows proper regulatory oversight.
