The UK has paused a clinical trial on puberty blockers after the medicines regulator raised safety concerns. The agency warned about unknown long-term biological risks and demanded a minimum age of 14.
The Medicines and Healthcare products Regulatory Agency will hold talks with King’s College London next week. The Department of Health and Social Care said recruitment will not start until they resolve the issues.
The study followed the Cass review, which found weak evidence for benefits in young people. Dr Hilary Cass said only a trial could clarify the treatment’s effects.
The government stressed that participant safety guides every decision. Clinicians will now examine the new evidence before the project continues.
King’s College London said young people’s wellbeing remains its priority. It will work with the regulator and defend the trial’s scientific rigour.
Researchers had planned to recruit more than 200 participants over three years. The original design allowed children as young as ten. The regulator now wants a stepwise approach starting at 14.
NHS England has already ended routine prescriptions of puberty blockers for gender dysphoria. Their use is now limited to research.
Professor Sir Jonathan Montgomery said the pause aims to improve the study design. He called it a normal safety measure that protects participants.
