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Dutch rollout

The Dutch Protocol — puberty suppression from early puberty, followed by cross-sex hormones and later surgery — was developed, according to the Cass Review, by Peggy Cohen-Kettenis, founder of the Utrecht clinic (source). It was taken up in the UK and internationally on the basis of a prospective study of 70 patients, one of whom died after surgery (source). In 2026 the Dutch Health Council noted that the approach applied in international practice does not always match the current Dutch care model (source).

The origins: Utrecht and the Dutch studies

Peggy Cohen-Kettenis's team saw minors in Utrecht from 1987 to 2002; the first case of puberty suppression was published in 1998 by Cohen-Kettenis and Van Goozen (source). The Dutch team's 2011 prospective study covered 70 patients who received puberty blockers between 2000 and 2008. Inclusion criteria were a minimum age of 12, life-long gender dysphoria that increased around puberty, psychological stability without serious comorbid psychiatric disorders, and family support (source). The 70 were a subset of 111 consecutively referred cases, chosen because they were the first ones ready for the next stage; the Cass Review notes that the outcomes of the remaining 41 were not reported. In the 2014 follow-up of 55 young adults (22 trans women and 33 trans men), gender dysphoria was alleviated and well-being was similar to or better than that of same-age young adults from the general population; one participant died after vaginoplasty, from necrotizing fasciitis (source). See VUmc protocol criticism for the full methodological analysis.

International transfer: a small cohort to a global standard

In 2007, Norman Spack established a clinic in Boston modelled on the Dutch protocol and began prescribing puberty blockers from early puberty (source). The UK trialled puberty blockers under a research protocol from 2011, in an uncontrolled study with inclusion criteria in line with the original Dutch protocol (same source). According to Cass, early versions of the Endocrine Society guideline (2009) and WPATH SOC7 influenced almost all other guidelines (paragraphs 9.20–9.22; same source). The review also notes that the current group is a different cohort from the group in earlier studies, and that the approach was later extended to a broader group of adolescents who would not have met the criteria of the original Dutch study (source). In England, referrals shifted from mostly boys before puberty to mostly girls in or after puberty, without a clear explanation (source); see the social media explosion and ROGD. The Cass Review rated the original study by De Vries et al. (2011) as of moderate quality, with no change in gender dysphoria (source).

The Dutch cohort under fire

In 2023, Michael Biggs published a review of the Dutch Protocol in the Journal of Sex & Marital Therapy. He argues that the main evidence came from a longitudinal study of 70 adolescents whose outcomes shortly after surgery appeared positive, except for the patient who died, but rested on a small number of observations and incommensurable measures of gender dysphoria, and that a replication study in Britain found no improvement (source, abstract). Abbruzzese, Levine and Mason (2023) published a critical evaluation of the Dutch studies in the same journal (source). The Cass Review (2024) notes that not all participants (59–73% on the various measures) completed questionnaires after treatment, and that all patients were seen regularly by a psychiatrist or psychologist, which makes it difficult to separate the effects of those sessions from those of the puberty blockers (source). Environmental Progress concludes from the WPATH Files (2024) that WPATH members know that children and young people cannot oversee the lifelong consequences of treatment; that is Environmental Progress's reading, and of the members contacted one person confirmed their own statements while another disputed the interpretation (source).

Current Dutch situation

On 30 June 2026 the Dutch Health Council (Gezondheidsraad) published its advice Transgenderzorg voor jongeren (Transgender care for young people). It concluded that somatic treatment of young people with gender dysphoria fits within the legal framework, that research shows the intended physical effects are achieved, that there are indications of some improvement in mental outcomes and that the number of cases of regret is low. It adds that the effects on cognition and fertility are insufficiently studied, that long-term data are lacking and that the number of people with regret cannot be reliably determined because of short follow-up and substantial attrition in studies (source). The Council notes that other countries often refer to the Dutch Protocol, but that international practice does not always match the current Dutch care model, which emphasises stepwise exploration of gender identity. In England and Sweden, puberty blockers and gender-affirming hormones are now available to young people only in research settings; in Germany, Austria, Switzerland, Poland and France they have recently been anchored more firmly in guidelines and expert statements (same source).

Since 2014, the Transgender Act has permitted the change of registered sex at the civil registry following an expert statement (Article 1:28 of the Civil Code; source). A bill that would have abolished the expert statement (Parliamentary Paper 35825, submitted in May 2021) was withdrawn by the cabinet in a letter of 11 August 2025, after the House of Representatives had asked for this by motion in April 2024 and again in April 2025 (source).

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