Amsterdam UMC and the Dutch Protocol
Amsterdam UMC (formerly VUmc) developed what became known as the Dutch Protocol from the 1990s onward: puberty blockers from Tanner stage 2, followed by cross-sex hormones from around age 16 and surgery from around age 18. For a long time, it was presented internationally as evidence-based. On re-examination, however, the original Dutch studies (De Vries, Steensma) turn out to have serious methodological limitations: small groups, no control group, substantial attrition, narrow selection criteria and the death of one participant after surgery. The claim that puberty blockers “are reversible and provide time to think” is no longer endorsed internationally; virtually all treated children go on to use cross-sex hormones.
How the protocol came about
The first publication on puberty suppression appeared in 1998, by Cohen-Kettenis and Van Goozen. In 2006, Delemarre-van de Waal and Cohen-Kettenis described the approach as a protocol: puberty blockers from age twelve, hormones from age sixteen and surgery from age eighteen. The premise was that blockers give a young person time to think while physical puberty is put on hold. More about the medication itself can be found on the page about puberty blockers.
The 2011 and 2014 studies
The evidence base consists mainly of two studies by the Amsterdam team. The 2011 outcome study followed 70 young people during treatment with puberty blockers. The 2014 follow-up study described 55 young adults after hormones and surgery. The researchers concluded that gender dysphoria had decreased and psychological functioning had improved. Clinics in other countries cited these two studies when they adopted the treatment.
What critics argue
In 2022, British sociologist Michael Biggs published an analysis of the origins and evidence base of the protocol. In 2023, an article by Abbruzzese, Levine and Mason followed, arguing that the Dutch studies are wrongly regarded as reliable. Their objections are that there is no comparison group, that the group was small and strictly selected, and that mainly the most favorable outcomes were reported. In the Zembla broadcast of October 26, 2023, methodologist Gerard van Breukelen of Maastricht University said that the absence of a comparison group was fatal to the question of whether the treatment works. How this criticism reached the Netherlands is explained in the article about international criticism.
The practitioners’ response
Child and adolescent psychiatrist Annelou de Vries of Amsterdam UMC told Zembla that a control group would be unethical, because young people who need treatment would then not receive it. She pointed out that more research has since been published. A 2022 study of 720 young people from the Amsterdam cohort who had started hormones after puberty blockers showed that 98 percent were still using those hormones at their last follow-up. Practitioners interpret this as evidence that few young people change their minds. Critics see it as an indication that blockers are not a neutral pause for reflection, but the first step in a medical pathway. How many referred young people start such a pathway is reported in the news article about young people referred to Amsterdam UMC.
Where things stand now
Since 2019, the approach has been set out in the Quality Standard for Somatic Transgender Care, which applies to all providers in the Netherlands. In 2024, the House of Representatives called for an investigation into treatment outcomes. On June 30, 2026, the Health Council concluded that care for young people is carefully organized, while also establishing that limited data are available on adverse effects; see the Health Council’s advisory report. The United Kingdom, Sweden and Finland weighed the same uncertainty as a reason for caution. Figures on the clinic’s patient numbers and waiting times can be found at trans-nederland.nl, on the page about Amsterdam UMC’s gender clinic.