Two UK clinical trials have been announced to investigate the impact of puberty blockers on young people with gender incongruence. The studies follow the 2024 Cass review, which found 'insufficient evidence' about the effects of puberty suppression on psychological wellbeing, cognitive development, and fertility.
The Pathways Trial will recruit an estimated 226 young people over three years, with the youngest participants expected to be aged 10–11 for biological females and 11–12 for biological males. Participants will be randomised to either start puberty blockers immediately or after a one-year delay, with their health monitored for 24 months.
A second study, Pathways Connect, will involve MRI brain imaging of about 150 trial participants and 100 young people not receiving blockers, comparing results with cognitive tests. Researchers say results will take at least four years.
Chay Brown of TransActual raised ethical concerns, calling the trial 'coercive' as it is the only NHS route to access blockers. He noted that the randomised design means some young people will experience distressing pubertal changes while waiting. Professor Emily Simonoff, chief investigator, argued that blockers should never have been offered outside a trial and that the study is the most ethical approach now.
