The Pathways Puberty Blocker Trial in England – What We Already Know About Puberty Blockers and Why This Trial in Unethical
- Emma D.
- Jan 24
- 10 min read
I am shocked that the Pathways Trial gained ethical consent; the trial plans to give puberty blockers to around 220 children (10-16 year olds but possibly as young as 8) experiencing discomfort with their sexed bodies (gender dysphoria). Puberty blockers were banned in the UK from being used for this purpose due to the serious health concerns linked to them.
The trial was recommended as part of the Cass Review into Gender Identity Services (GIDS) for children in England. The Cass Review also recommended a follow up to the 2000 children already prescribed puberty blockers through GIDS in England since 2014: There was no long-term follow up of the health outcomes for these children who will now be young adults.
We still don’t have this data and my view is that it would be unethical to give these drugs to more children when we have limited information about the long term affects of their use.
From what I can gather from reading articles assessing the trial protocol the main drive for this trial is because there are children and their parents who believe it is medically necessary and that they might seek these drugs through the black market otherwise.
As I have noted before; surely it is better to give children the emotional and mental health support to accept and live happily in their healthy bodies than give them experimental drugs which risk their long term health? There is no medical purpose for giving these drugs for children experiencing distress at their sexed bodies. They do not have any physical illness which needs treating. The £10 million funding for the trial could pay for improved mental health services for many more than 220 children.
What Are Puberty Blockers?
Puberty blockers are a type of medication called gonadotrophin-releasing hormone (GnRH) analogues. They are licensed only for use in young children (for precocious puberty) or older adults (for certain cancers).
They are not licensed for use in adolescents and they are not licensed for gender incongruence or dysphoria.
Licensing of medicines requires a robust assessment of safety and effectiveness data. These medications have not undergone that process, which means the safety and risk implications for use with gender dysphoria have not been assessed.
Use For Precocious Puberty Vs Use for Gender Dysphoria:
Precocious puberty is diagnosed when a girl under 8 or boy under 9 begins developing secondary sex characteristics (pubic hair, breast development, penis and testicles growing bigger). Treatment with puberty blockers is only given if it is thought there’ll be an impact on a child’s emotional or physical health; early puberty can cause issues with bone density and height growth, there can also be a psycho-social impact eg on peer relationships, or girls as young as 5 having to manage menses.
In cases of precocious puberty blockers are only given until the child reaches the age at which puberty would normally start so they then go through puberty within the expected time range.
Their use for Gender Dysphoria is unlicensed and experimental and is based on a study known as ‘The Dutch Protocol’ in the early 2000s. 98% of the children in the original study went on to take cross –sex hormones, so never went through puberty. Prior to this nearly all children (60-80%) who had experienced distress at their sex and wanted to be seen as the other sex desisted and were comfortable in their sexed bodies following puberty. Most of these children grew up to be gay or lesbian. In these earlier studies (from the 1970s – 1990s) researchers did not find any way to differentiate or identify which children would persist with a cross-sex identity (transgender) in adulthood.
Their use in England began in 2011 following pressure on GIDS by parents and activist groups who had become aware of their use in the Netherlands. GIDS repeated the Dutch study but did not get the same results.
The Dutch Protocol/ The Dutch studies:
Professor Michael Biggs (Oxford University) has an in depth essay about the Dutch studies here which covers the full history of the use of puberty blockers for children with gender identity disorder (as gender dysphoria was called originally). The only patient who had any long term follow up was the first patient; Dutch clinicians Cohen-Kettenis and Delemarre-van de Waal worked with a girl who wanted to be a boy. Her father wasn’t happy about her masculine presentation (she was a tomboy from a young age) and she grew up to be attracted to girls. She was given puberty blockers aged 13 in around 1987 then testosterone at 18 followed by surgeries to remove her breasts, ovaries and womb and a metoidioplasty (surgery to alter the appearance of her genitals to appear masculine). Aged 20 (around 1994) the patient was happy, but when followed up again at age 35 she (now he) scored high on the measure for depression, had shame around ‘his’ genital appearance and was unable to sustain a romantic relationship. In interviews aged 48 ‘he’ was now in a long term relationship, working and content so a positive outcome in terms of emotional health, but long term physical outcomes are still unknown.
The Dutch Protocol was published in 2006; there were strict criteria for children to be accepted onto it:
1) No other underlying mental health issues
2) Gender dysphoria since early childhood which worsened at the onset of puberty
3) Family support.
Puberty blockers could be prescribed at Tanner stage 2 (first growth of pubic hair) at a minimum age of 12. Cross sex hormones (testosterone for girls, oestrogen for boys) could then be given at 16 and surgeries at 18.
The stated goal of this treatment was to allow the child to ‘pass’ better in adulthood ie to appear more like the sex they want to be; Cohen-Kettenis got the idea for earlier medical intervention by comparing the patients she had helped to ‘transition; in their 20s with those who had transitioned as older adults.
Annelou De Vries completed a longitudinal study of 70 adolescents referred to the Dutch clinic between 2000 and 2008 and published the results in two papers in 2011 and 2014 which found that “gender dysphoria had resolved, psychological functioning had steadily improved, and well-being was comparable to same-age peers” (de Vries et al. 2014).
Outcome measures were taken 3 times; before treatment, after puberty suppression but before cross-sex hormones and after surgery. Outcome measures used were behavioural and emotional problems, depressive symptoms, anxiety and anger, general functioning, gender dysphoria and body satisfaction.
Criticisms of the Dutch Study
Not all 70 adolescents were followed up – at the final stage 15 were not participating; 6 were waiting for surgery, 2 refused to participate, 2 didn’t return questionnaires, 1 left care and 3 weren’t medically fit for surgery due to obesity or diabetes. There is no consideration in the study as to whether their medical issues could have been caused by the puberty blockers or cross-sex hormones. It is interesting to note here that Jazz Jennings also became obese after starting on puberty blockers.
One teenager died of necrotizing fasciitis as a result of surgery; vaginoplasty is very difficult to perform on boys who have had their puberty suppressed as there isn’t enough penile tissue to work with, so surgeons use part of the colon to create the appearance of a vagina – this has increased risk of infection.
Impact on health was not studied
Follow up ended 1 year after surgery (an average age of 20.7) so long term outcomes are not known.
The questionnaires used to measure gender dysphoria were swapped so at the start of the study boys were given the questionnaires for males which asked how they felt about their male body then later in the study were given the questionnaires for females which asked how they felt about the female body (including menstruation). Girls were given the female questionnaires initially and the male ones later in the study (they were completed at 3 times).
The results of the study have never been replicated; the Tavistock GIDS followed the same study protocol from 2011-2014 with 44 adolescents who were given puberty blockers, the full study results weren’t published until 2021 after a protracted campaign for their release. There was no improvement in gender dysphoria or psychological functioning.
In the Tavistock study 43 of the 44 children went on to take cross sex hormones, which is consistent with the results of the Dutch study.
What We Know About Side Effects/ Health Risks:
For Precocious Puberty
Even when used for precocious puberty there are potential effects on physical and mental health; their use can lead to reduced bone density, depression and low mood. A number of women treated for early puberty with a specific blocker called Lupron found they were suffering health issues as adults including fibromyalgia, problems with their teeth, jaws and bones.
Studies into the long term effects of taking puberty blockers for precocious puberty found “conflicting results have been published on the long-term effects of GnRHa therapy in patients with CPP (Central Precocious Puberty). These included a higher incidence of polycystic ovary syndrome (PCOs), changes in body composition, metabolic profiles and bone mineral density. Moreover, short term side effects such as headaches, hot flushes, mood swings and injection site reactions (rashes, bruising and sterile abscess formation) have been reported in the literature.”
On the whole when blockers are used for precocious puberty there isn’t an impact on long term bone density but this is dependent on the child going through puberty at the crucial stage for bone development so future problems may depend on the length of time and the age at which they are given.
For Gender Dysphoria
There was no follow up for any of the approximately 2000 children prescribed puberty blockers by GIDS in England so the risks are still unknown. The Cass Review carried out a systematic evidence review of all studies into the use of puberty blockers for gender dysphoria which found no strong evidence for the use of puberty blockers and there have been no studies into the long term effects.
Criticisms of the Pathway Study Design
As with previous studies the Pathways study design only follows the children for a period of 2 years, so once again the impact on long term health will not be studied. Other criticisms of the study design include the lack of a hypothesis as a basis for the study and a focus on self-reported satisfaction and wellbeing rather than health.
The study design claims it is a Randomised Control Trial however there is no control group; all the children will be given puberty blockers, the only difference being that one group will be given them a year before the other group.
The study does include looking at the impact on cognitive functioning and bone health, but again there is only a year difference between the 2 groups to look at.
Previous research has consistently shown that nearly all children given puberty blockers go on to take cross-sex hormones; this means that the long term health issues caused by these should also be taken into account when considering how ethical this study is. The known effects of high levels of oestrogen on males include higher risks of stroke, blood clots, diabetes, breast cancer, ms and infertility. The known effects of high levels of testosterone on women include early menopause, vaginal atrophy, increased risk of heart disease and increased risk of cancer.
Conclusion
If the child goes straight onto cross-sex hormones from puberty blockers they will not go through a natural puberty and there is no research which comprehensively covers the outcomes of this pathway. I can understand that this could be seen as an argument to carry out this research, but is it a good enough reason and does the research study take account of this?
For me the more ethical approach would be for the government to prioritise a study into the health outcomes of those 2000 young adults who have already followed this pathway.
Are they physically healthy? Are they mentally healthy? What medication are they on? How does their cognitive functioning compare with a cohort of similar adults who did not follow the pathway of puberty blockers followed by cross-sex hormones? How many of those adults did not go on to take cross-sex hormones and what are their outcomes? Is there a significant difference between their health and the health of those who did go on to take cross-sex hormones?
The Pathways study states that a retrospective study wouldn’t provide the evidence needed. I disagree with this; the health outcomes could be compared to the health outcomes of the general population at a similar age which would give a good indication of the health and mental health impact of this Pathway (puberty blockers followed by cross sex hormones). It wouldn’t give the specific data regarding puberty blockers alone, but it is clear from all current research that the majority of teens taking blockers go on to take cross-sex hormones.
Puberty IS difficult and any child suffering has my empathy; I had issues with my own mental health throughout puberty and in my 20s. The evidence points clearly to the majority of these children being same sex attracted and that for most of these children their dysphoria will resolve during puberty. Why risk their long term health outcomes and a future in which they always have to take cross-sex hormones to appear as the opposite sex, rather than give them mental health support until they reach adulthood and can make those decisions then?
Puberty is a time of great changes both physically and mentally; it is a time when the pre-frontal cortex (responsible for decision making) is ‘re-wiring’ leaving teenagers prone to impulsive, risk-taking behaviour and rigid thinking. This is not a time to be making health decisions with such serious life-long consequences unless their life is at risk otherwise (eg from cancer).
Initially the rhetoric was that these children are at high risk of suicide and puberty blockers are ‘life saving’. This has been debunked, and this rhetoric puts children at risk due to what we know about suicide and the need for caution when reporting any suicides due to people copying.
Parents and teens were also told that puberty blockers are fully reversible; this was based on them being giving to a different cohort at a different time developmentally (children experiencing precocious puberty); these children then went through puberty at the expected age. The truth is no-one knows what impact of taking blockers throughout puberty does; there are probably children who started taking them then stopped as young adults without going on to cross sex hormones, but they were never followed up.
Actions You Can Take:
Sign the petition to cancel the trial https://petition.parliament.uk/petitions/751839
Sign the Genspect Statement of Concern https://genspect.org/puberty-blocker-trial/
Join us at EBSWA: The Evidence Based Social Work Alliance
Further reading & Listening:
Genspect: Stop The NHS Puberty Blocker Trial https://genspect.org/puberty-blocker-trial/
Letter from Clinicians concerned about the trial: https://can-sg.org/can-sg-letter-to-pathways-puberty-blocker-trial-investigators-oversight-board-and-regulators/
Dutch puberty-blocker pioneer: Stop “blindly adopting our research” https://4thwavenow.com/2021/03/16/dutch-puberty-blocker-pioneer-stop-blindly-adopting-our-research/
The Dutch Model is Falling Apart: https://genspect.org/the-dutch-model-is-falling-apart/
Risks of Puberty blockers: https://biologicalintegrity.org/wp-content/uploads/2023/09/Fact-Sheet_-Risks-of-Puberty-Blockers.pdf
Systematic Reviews into the use of Puberty Blockers for Gender Dysphoria: https://segm.org/NICE_gender_medicine_systematic_review_finds_poor_quality_evidence
Gender A Wider Lens Podcast 101 Michael Biggs on Puberty Blockers: From Curiosity to Exposé
Women’s Rights Network Podcast: Talking about the Puberty Blockers trial with Louise Irvine and Terry Patterson (from CAN-SG Clinical Advisory Network on Sex & Gender and Thoughtful Therapists)
Sources:
Biggs M. (2022) The Dutch Protocol for Juvenile Transsexuals: Origins and Evidence https://www.tandfonline.com/doi/full/10.1080/0092623X.2022.2121238#abstrac
De Sanctis et al (2019) Long-term effects and significant adverse drug reactions (ADRs) associated with the use of gonadotropin-releasing hormone analogs (GnRHa) for central precocious puberty: a brief review of literature https://pmc.ncbi.nlm.nih.gov/articles/PMC7233750/
De Vries et al (2011) Puberty Suppression in Adolescents with Gender Identity Disorder: A Prospective Follow Up Study https://www.webofscience.com/wos/woscc/full-record/WOS:000293185500017
De Vries et al (2014) Young Adult Psychological Outcome After Puberty Suppression and Gender Reassignment https://publications.aap.org/pediatrics/article-abstract/134/4/696/32932/Young-Adult-Psychological-Outcome-After-Puberty?redirectedFrom=fulltext & https://www.fundacionjuntoscontigo.org/estudios/bloqueadores.pdf
Jewett C. (2017) Drug used to halt puberty in children may cause lasting health problems https://www.statnews.com/2017/02/02/lupron-puberty-children-health-problems/
Kings College London (2025) PATHWAYS Trial Protocol v2.2 20.11.2025 Puberty Suppression and Transitional Healthcare with Adaptive Youth Services (PATHWAYS) https://www.kcl.ac.uk/ioppn/assets/pathways/trial/pathways-trial-protocol.pdf
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