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Cass Review of puberty blockers: no pause button, a one-way street

Puberty blockers — GnRH agonists such as leuproreline (Lupron) and triptoreline — have been used since the Dutch Protocol to halt puberty in children with gender dysphoria. The Cass Review delivers a scathing verdict: no evidence of psychological benefit, no suicide prevention, and the "pause button" does not exist — 97 percent of children receiving blockers progress to cross-sex hormones. Blockers are not a pause for thought; they are the first step in a medical one-way street.

What are puberty blockers?

GnRH agonists inhibit the hypothalamic-pituitary-gonadal axis and stop the production of sex hormones. They are registered for use in oncology and for central precocious puberty. They have never been registered for gender dysphoria — their use is entirely off-label, in a population for which no registration study has ever been conducted.

What does the Cass Review say?

The systematic review by the University of York examined 50 studies on puberty blockers. One met high quality standards; 49 fell under low or very low GRADE quality. Concrete conclusions:

• No evidence that blockers improve psychological functioning.
• No evidence that they prevent suicide — the most cited claim of the affirmative field is unsubstantiated.
• 97 percent of children who receive blockers progress to cross-sex hormones. No "pause button" — a stepping stone.
• Known risks: loss of bone density, possible effect on brain development, sterilization with combined hormone treatment.

The pause button is a myth

The claim that blockers "provide a pause to think" has been factually falsified by the Cass Review. Those who receive blockers do not remain in a developmentally neutral moment — they are placed on a trajectory that almost everyone stays on. Moreover, by halting puberty, natural desistance is rendered impossible: the child can no longer experience what becoming an adult would mean within their own body. Blockers are an intervention that actually perpetuates the problem they are supposed to investigate.

The NHS decision and the international turnaround

In March 2024, the NHS discontinued puberty blockers outside of a research setting for young people with gender dysphoria; Scotland and Wales followed suit. GIDS closed in 2024. Sweden (SBU 2022) , Finland (COHERE 2020) , Norway (Ukom 2023) , and Denmark (2023) had already moved in the same direction earlier. Four Scandinavian countries plus the UK — independent and evidence-based — have phased out puberty blockers as routine treatment for minors. Only the Netherlands persists.

The Dutch Protocol: one study, seventy children, scaled up worldwide

The original Cohen-Kettenis study from 2011 involved 70 carefully selected adolescents. One committed suicide after vaginoplasty. The study had no control group, a short follow-up, and has never been replicated since. Yet this became the global model — a scaling up that was never justified. See criticism of the VUmc protocol and the broader Dutch rollout .