The UK has suspended a clinical trial on puberty blockers for young people after the medicines regulator raised safety concerns. The regulator warned about unknown long-term biological risks and called for 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 confirmed that recruitment will not begin until they resolve the issues.
The study followed the Cass review, which found weak evidence for the treatment’s benefits. Dr Hilary Cass said a controlled trial was necessary to clarify the effects despite strong beliefs in the medication.
The health department said participant safety remains the main condition for approval. Experts will review the evidence before the trial can proceed.
King’s College London said the project aims to build a reliable evidence base. The university will work with the regulator during the review.
Researchers had planned to recruit 226 participants within three years. The original design allowed children as young as ten. The regulator now wants a step-by-step approach that starts at 14 because of uncertain risks.
NHS England has already ended routine use of puberty blockers for gender dysphoria. Their use now remains limited to research.
Professor Sir Jonathan Montgomery said the pause strengthens the study rather than stops it. He called the move a proper focus on safety.
