The Dutch Protocol

In the Netherlands, services for children and adolescents with gender incongruence date from 1987 (source). The approach later known as the Dutch Protocol was developed by Peggy Cohen-Kettenis, founder of the Utrecht clinic; in 1998 she and van Goozen, then at the academic hospital in Utrecht, published a case study of a girl who had started puberty blockers at age 13 (source). The first outcome study (de Vries et al. 2011) covered 70 adolescents; de Vries et al. 2014 reported on 55 of them. Neither had a control group, and the Cass Review rated the 2011 study as of moderate quality, with no change in gender dysphoria (source). The Endocrine Society guideline and WPATH SOC 7 influenced almost all other guidelines, few of which were based on a systematic review of the evidence (source).

At the Tavistock GIDS in the UK fewer than 50 children were seen per year before 2009; from 2014 referrals rose exponentially to roughly 5,000 in 2021/22, a figure that according to the Cass Review may include double counting (source). According to the Cass Review the current group is a different cohort from that of the earlier studies, and the approach was extended to a broader group of adolescents who would not have met the criteria of the original Dutch study (source). In her foreword Cass called the debate exceptionally toxic and wrote that in few other areas of healthcare are professionals so afraid to discuss their views openly (source).

The debate became visible in detransition research, in the WPATH Files (according to Environmental Progress, members know that children and adolescents cannot grasp the lifelong consequences of treatment; that is the reading of Environmental Progress — of the members approached, one confirmed his own statements and another disputed the interpretation) (source), and in court cases like Bell v Tavistock (the High Court ruled against the clinic in December 2020; the Court of Appeal allowed the clinic's appeal on 17 September 2021 (source)). In March 2024, before the Cass final report of April 2024, NHS England decided that puberty blockers are no longer available as a routine commissioning treatment option for under-18s (source).