The World Professional Association for Transgender Health (WPATH) has suppressed evidence that contradicts its policies, influenced by activist clinicians. Unsealed documents reveal WPATH’s efforts to control Johns Hopkins University’s research findings and remove age thresholds for treatments. WPATH’s guidelines lack rigour and evidence transparency, and its influence in the World Health Organization transgender guideline development group poses reputational risk to WHO. The revelations suggest a need for health providers to disassociate from WPATH’s influence to avoid potential harm and legal issues.