UK puberty blocker trial sets minimum ages of 11 and 12

A major clinical trial investigating the effects of puberty blockers on young people in the UK is set to begin recruitment in August, following the resolution of a months-long safety dispute with the national medicines regulator. The Pathways Trial, led by King’s College London, will now proceed with new minimum age requirements of 11 for birth-registered females and 12 for birth-registered males.

The trial was originally launched in late 2025 but was suspended indefinitely in February 2026 after the Medicines and Healthcare products Regulatory Agency (MHRA) raised significant safety concerns. In correspondence with researchers, the regulator warned of a "very likely" risk of fertility loss and permanent damage to bone health, as well as "potentially significant and, as yet, unquantified risk of long-term biological harms." The MHRA had initially recommended raising the minimum participation age to 14, where none had previously been formally set.

Following extensive discussions, the MHRA announced last week that it had approved a modified protocol with strengthened safeguards. These include the newly established age limits, more clearly defined criteria for discontinuing...