Video: Puberty blockers for gender dysphoria: The Dutch protocol

Dr. Michael Biggs


In the UK on December 1st 2020 the High Court handed down judgment on the use of puberty blockers for the treatment of children under the age of eighteen.

puberty blockers

The judicial review was brought by former Tavistock psychiatrist Susan Evans against the Tavistock & Portman NHS Trust. The claimants were Keira Bell, a 23 year-old young woman who regretted the medical intervention she underwent at the Tavistock Gender Identity Development Service, and Mrs A, the mother of an autistic 15 year-old girl who was waiting for treatment. The claim brought before the court was that a child under the age of eighteen cannot give informed consent to treatment with puberty blockers.

This was the court’s conclusion.

puberty blockers

The full court judgment can be read here. In 2021 the Tavistock GIDS won their appeal against this judgment. The Appeal Court judged that informed consent was not a matter to be decided by law, but by clinical and medical professionals. However, this judgment does not negate the findings of the Divisional court based on the evidence presented by both sides, it simply says that it is not the court’s place to make such decisions. An appeal against this judgment was denied so the case will not proceed to the Supreme Court.

What are puberty blockers? 

Puberty blockers are a class of synthetic gonadotrophin-releasing hormone (GnRH) analogues. By acting on the pituitary gland, these drugs prevent the release of chemical signals which stimulate the production of estrogen and testosterone, halting the changes of puberty caused by these sex hormones.

The Tavistock GIDS began an ‘Early Intervention study’ in 2011. Previous to this, puberty blockers were offered as a treatment only to children from the age of sixteen. The trial lowered the age to twelve, and subsequently, by 2014, to any child who had reached Tanner Stage 2 of puberty. This meant that now children as young as ten could be given blockers. To date GIDS has treated over a thousand children with puberty blockers, with about 230 of these children under the age of 14, the youngest child being 10 years old. 

The claimed therapeutic benefit is to allow more time for children to consider whether they want to continue transitioning via cross-sex hormones and surgery, without the stress of ongoing unwanted pubertal development. Those who choose not to transition can stop taking blockers, and it is claimed that their original puberty will resume and progress normally. It was claimed that the drugs are effective, safe and fully reversible.

Is there any evidence to back up this claim?

The NHS has changed their guidance on puberty blockers. From previously claiming that blockers “are considered to be fully reversible” the NHS webpage now states:

“Little is known about the long-term side effects of hormone or puberty blockers in children with gender dysphoria.

Although the Gender Identity Development Service (GIDS) advises this is a physically reversible treatment if stopped, it is not known what the psychological effects may be.

It’s also not known whether hormone blockers affect the development of the teenage brain or children’s bones. Side effects may also include hot flushes, fatigue and mood alterations.”

Side effects of puberty blockers

GnRH analogues were first licensed for use as end-stage prostate cancer drugs in 1985 and are still in widespread use today. They are also prescribed to chemically castrate sex offenders in Broadmoor. They have since been used in other indications and are most recently being used ‘off-label’ to delay puberty in children with gender dysphoria. They are also used by transgender adults on cross-sex hormone therapy to suppress the production of their natural sex hormones.

In the US, a GnRH analogue drug with the tradename Lupron was licensed in 1993 for use in children with precocious puberty.  It was also commonly used off-label to help children who needed to grow taller. There is now a growing number of women who used Lupron in childhood who are reporting serious issues with bone and blood disorders and joint problems in adulthood. This information is reviewed here.

It has long been known that mechanistically GnRH analogues can cause bone thinning. The reduction of estrogen levels in girls can induce a temporary osteopenia (similar to what’s seen in menopause when estrogen levels naturally fall). A 2009 study showed that Lupron caused bone thinning in girls treated although bone density was seen to return to normal levels within 10 years after treatment. There is also a large 2005 study in men treated for prostate cancer in which a significantly increased risk of bone fractures was observed. The bone thinning effects are also mentioned in the ‘Important safety information’ leaflets that accompany Lupron and extended use is not recommended in people with pre-existing bone thinning conditions.

The FDA considers the drug’s impact on children’s bones an unanswered question, according to a statement: “The effects of bone density in children whose central precocious puberty is arrested with a GnRH agonist are considered ‘unknown’ as they have not been studied”

A groundbreaking documentary by the state-run television channel in Sweden has revealed a shocking case of bone damage on one child, Leo. Leo is one of 13 children treated by the Karolinska University Hospital who are known to have suffered catastrophic injuries as a result of puberty blockers.

Their ailments include liver damage, unexplained weight gains of up to two stone, mental health problems, skeletal damage and a failure to grow.

The full documentary, part of the Trans Train series, can be watched at this link:

Leo’s case was reported in the Daily Mail.

“Leo is in pain most of the time. His back hurts badly when he stands up or walks. It is a hard life for a teenager, and he has no idea if the agony will ever go away.

Leo has spinal fractures and a condition called osteopenia, which weakens the bones, making them more liable to break. It is a disease that you often see in people aged 60 or 70 and is almost impossible to reverse.”

The UK endocrinologists at GIDS use the GnRH analog called Triptorelin. Although slightly different to Lupron all these drugs are in the same class of GnRH analogs and all have the same mechanism of action. The mechanistic safety issues will most likely apply to the whole class of drugs.

Triprorelin is manufactured by two different companies under the tradenames Gonapeptyl Depot and Decapeptyl SR. This drug has been approved by NICE for use in children with precocious puberty, although it should be noted that it is being used ‘off label’ for children with gender dysphoria. This means its use by the NHS does not come with regulatory approval because the appropriate safety studies are not available.

Leuprorelin (Lupron) has not been approved by NICE for use in children. This is only prescribed if adverse reactions are observed with Triptorelin. GIDS prescribing information was made available under a freedom of information request here.


What is the longer term impact on gender identity?

puberty blockers


Although blocking the progression of puberty can in some cases relieve the immediate distressing symptoms suffered by children with gender dysphoria, the evidence is mixed. The long term effects are unknown. There have been no long term studies on the effectiveness of puberty blockers and it is unknown whether interrupting natural puberty alters the natural trajectory and perhaps resolution of gender dysphoria in children.

Gender identity is shaped during puberty and adolescence as young people’s bodies become more sexually differentiated and mature. Given how little we understand about gender identity and how it is formed and consolidated, we should be cautious about interfering with the normal process of sexual maturation.

What we do know however is that virtually all the children who start on puberty blockers eventually go onto cross-sex hormones suggesting that changing their minds is rare once natural puberty is interrupted.

The Tavistock’s own published study on their Early Intervention trial shows that of 44 children given puberty blockers, 43 (98%) progressed to cross-sex hormones. The overall finding of the study was that GnRHa treatment brought no measurable benefit nor harm to psychological function in these young people with gender dysphoria. An analysis of the study results by Michael Biggs can be read here.

The Health Research Authority, in its investigation into the Tavistock’s Early Intervention study, questioned the stated purpose of puberty suppression as providing children with ‘space to decide’. The HRA report suggested  that blockers were in fact used as a first step towards further medical intervention in the form of cross-sex hormones:

It would have reduced confusion if the purpose of the treatment had been described as being offered specifically to children demonstrating a strong and persistent gender identity dysphoria at an early stage in puberty, such that the suppression of puberty would allow subsequent cross-sex hormone treatment without the need to surgically reverse or otherwise mask the unwanted physical effects of puberty in the birth gender.

Cross-sex hormones have serious lifelong effects which cannot be reversed if treatment is discontinued. If a child takes puberty blockers at Tanner stage 2 of puberty followed by cross-sex hormones at age 16 they will be sterilised as gametes have not developed.

Are the effects on puberty really reversible?

Since its rare for children with gender issues to stop taking puberty blockers this also means there have been no long term studies to show that normal puberty will resume in these children. The evidence of ‘reversibility’ is from studies in a different set of children; namely children with precocious puberty (a puberty disorder in which puberty commences very early. Technically this is before the age of 8 in girls but could be as young as pre-school age). In these children puberty blocking drugs are normally withdrawn around the age of 12 and menstruation in girls commences about 1 year later. In this respect the resumption of puberty occurs around the ‘expected age’ in children and will be in line with other aspects of physiological and psychological adolescent development.

This is very different from the approach in children with gender dysphoria. Normal puberty is postponed while the normal ageing process proceeds. Restarting natural puberty would therefore be out of step with other development processes. It should also be noted that virtually all cases of precocious puberty occur in girls so there is extremely little evidence of the restarting of puberty in boys. For these reasons the true reversibility of blocking puberty in children with gender issues is currently unknown.

What are the implications of preventing a natural puberty? 

Proponents of the use of puberty blockers say that not only do these drugs relieve the distressing symptoms of ‘the wrong puberty’ in childhood but also prevent the body from undergoing irreversible changes which then have to be modified surgically during adulthood. For example, permanent growth of breasts in females which may necessitate a double mastectomy in the future. Alternatively, permanent facial hair growth in males which may necessitate its removal in the future. However, what is rarely discussed is the effect on the reproductive and sexual development of the child.

Puberty blockers followed by opposite sex hormones cannot create ‘opposite sex puberty’, only secondary sex characteristics of the opposite sex. However, normal sexual or reproductive development will not occur. Girls will not begin menstruation and so will be infertile. Boys testes will not grow and develop and will impact on fertility. The change therefore is only cosmetic. A boy’s penis will remain immature and remain the size of a child’s into adulthood. This will cause problems sexually if the penis is retained, both functionally and in terms of sexual arousal. It is also problematic if gender reassignment surgery is later chosen since there is too little material to use from the penis and testicles. 

When a child’s natural puberty is blocked we can expect to see effects not only on the body but on the developing brain. It is the surge of sex hormones at puberty which triggers the important changes in the adolescent brain which only reach completion in the mid-twenties. Hormonal changes at puberty  are thought to influence the development of both brain structure and function.

Recent research indicates that there is a window of development for some cognitive functions, and if this window is missed, cognitive development does not resume later even if blockers are discontinued. A reduction in long-term spatial memory was found to persist after discontinuation of blockers in a recent study on sheep, which concluded:

This result suggests that the time at which puberty normally occurs may represent a critical period of hippocampal plasticity. Perturbing normal hippocampal formation in this peripubertal period may also have long lasting effects on other brain areas and aspects of cognitive function. 

Two previous studies which analysed IQ performance in girls taking puberty blockers for central precocious puberty also suggest the possibility that GnRHa treatment may have an adverse impact on cognitive functioning in children. The first study of 25 children in 2001 found a drop of 7 IQ points after two years on blockers. The second study in 2016 found a drop of 8 IQ points in 15 girls compared to a matched control group. An analysis of these studies is here.

A study in 2017 of men with late stage prostate cancer found that treatment with GnRH analogs affects cognitive functions such as language ability, short-term memory capacity, mental flexibility, and inhibitory control.

A recent analysis of evidence by Professor Michael Biggs, who researched the Tavistock GIDS Early Intervention study, indicated some significant and worrying emotional/behavioural effects reported after children had taken puberty blockers for a year:

‘Natal girls showed a significant increase in behavioural and emotional problems’, according to their parents (also from the Child Behavior Checklist, contradicting the only positive result). One dimension of the Health Related Quality of Life scale, completed by parents, ‘showed a significant decrease in Physical well-being of their child’. What is most disturbing is that after a year on blockers, ‘a significant increase was found in the first item “I deliberately try to hurt or kill self”’ (in the Youth Self Report questionnaire).

In a review of all recent published research studies, Professor Carl Heneghan highlighted the very low quality of evidence for the benefits of blockers:

Problems within these studies, however, make it difficult to assess whether early pubertal changes regress under GnRHa treatment and whether prolonged puberty suppression is safe. For example, there is a lack of controls, and in one study that included controls, these were inadequate as relatives and friends of the participants were asked to participate, serving as age-matched controls. A  lack of blinding was also problematic. 

The conclusion on the evidence for all ‘gender affirming’ treatment for children and young people was this:

Treatments for under 18 gender dysphoric children and adolescents remain largely experimental. There are a large number of unanswered questions that include the age at start, reversibility; adverse events, long term effects on mental health, quality of life, bone mineral density, osteoporosis in later life and cognition.

The National Institute for Health and Care Excellence (NICE) published two evidence reviews in 2020 on treatments for children and adolescents with gender dysphoria.

The conclusion of the evidence review of Gonadotrophin releasing hormone analogues for children and adolescents with gender dysphoria was:

“The results of the studies that reported impact on the critical outcomes of gender dysphoria and mental health (depression, anger and anxiety), and the important outcomes of body image and psychosocial impact (global and psychosocial functioning) in children and adolescents with gender dysphoria are of very low certainty using modified GRADE. They suggest little change with GnRH analogues from baseline to follow-up.”

There are a number of recent ‘studies’ which purport to show that puberty blockers ‘cure’ suicidality. The most recent has been widely publicised. Read Michael Biggs’ analysis to see how the study results do not back up the claims of the authors.

Puberty Blockers and Suicidality in Adolescents Suffering from Gender Dysphoria 

The independent NHS-commissioned Cass Review of the Tavistock GIDS published its interim report in March 2022. This is what the report had to say on the subject of puberty blockers:

‘There has been research on the short-term mental health outcomes and physical side effects of puberty blockers for this cohort, but very limited research on the sexual, cognitive or broader developmental outcomes.

In the short-term, puberty blockers may have a range of side effects such as headaches, hot flushes, weight gain, tiredness, low mood and anxiety, all of which may make day-to-day functioning more difficult for a child or young person who is already experiencing distress. Short-term reduction in bone density is a well-recognised side effect, but data is weak and inconclusive regarding the long-term musculoskeletal impact.

The most difficult question is whether puberty blockers do indeed provide valuable time for children and young people to consider their options, or whether they effectively ‘lock in’ children and young people to a treatment pathway which culminates in progression to feminising/ masculinising hormones by impeding the usual process of sexual orientation and gender identity development. Data from both the Netherlands and the study conducted by GIDS demonstrated that almost all children and young people who are put on puberty blockers go on to sex hormone treatment.

A closely linked concern is the unknown impacts on development, maturation and cognition if a child or young person is not exposed to the physical, psychological, physiological, neurochemical and sexual changes that accompany adolescent hormone surges. It is known that adolescence is a period of significant changes in brain structure, function and connectivity.

During this period, the brain strengthens some connections (myelination) and cuts back on others (synaptic pruning). There is maturation and development of frontal lobe functions which control decision making, emotional regulation, judgement and planning ability. Animal research suggests that this development is partially driven by the pubertal sex hormones, but it is unclear whether the same is true in humans. If pubertal sex hormones are essential to these brain maturation processes, this raises a secondary question of whether there is a critical time window for the processes to take place, or whether catch up is possible when oestrogen or testosterone is introduced later.

An international interdisciplinary panel has highlighted the importance of understanding the neurodevelopmental outcomes of pubertal suppression and defined an appropriate approach for investigating this further. However, this work has not yet been undertaken.’

Recently even the pioneer ‘gender affirming’ surgeons in the US have spoken out about the risks of putting children onto puberty blockers. Marci Bowers, who transitioned at the age of 38, admitted that children who undergo transition before puberty will never have adult sexual function or experience orgasm.

‘”An observation that I had,” said Bowers, “every single child who was, or adolescent, who was truly blocked at Tanner stage 2,” which is the beginning of physical development, when hormones begin their work of advancing a child to adulthood, “has never experienced orgasm. I mean, it’s really about zero.”‘

‘Bowers said that an additional concern is that when a boy child undergoes this process, the penis does not grow, which makes it hard to take that genital material and surgically give it the appearance of the genital area of the opposite sex.’

There are increasing concerns about potential irreversible effects of puberty blockers on children’s brain development. Studies on children given blockers for precocious puberty have indicated a potential drop in IQ points, with no evidence that these effects are fully reversible. A 2024 paper by Sallie Baxendale, The Impact of Suppressing Puberty on Neuropsychological Function, analyses these studies along with animal research and concludes:

“Whilst no means conclusive due to the poor quality of evidence, studies examining the impact of puberty suppression in young people indicate a possible detrimental impact on IQ. These findings concord with the wider literature on GnRH expression and brain structure and function.” 


It is often claimed that the use of puberty blockers in children is completely safe and reversible. This claim however has never been tested in long term studies and its use for gender dysphoria is experimental. What the evidence does show is that blockers may simply lock children into a medical pathway resulting in sterility and loss of sexual function.


NHS England announced on 12 March 2024 that puberty blockers will no longer be available on the NHS for children with gender-related distress, except as part of a clinical trial, subject to ethical approval. This new policy is in line with updated policies in Sweden  and Finland. New recommendations have also been issued in France. In the Netherlands, home of the “Dutch protocol”, a motion has been passed in the Dutch parliament for the government to investigate the research on puberty blockers.

For the full story of the Tavistock’s Experimentation with Puberty Blockers, download our free pdf of all five of Michael Biggs’ articles written for Transgender Trend. 



Further reading on the Bell & Mrs A v Tavistock judicial review:

Keira Bell’s Full Statement in Response to the High Court Judgment

Keira Bell statement

Interview with Susan Evans on the outcome of the Judicial Review 

Why I was right to blow the whistle on the Tavistock Clinic over puberty blockers 

Transgender Trend Response to the High Court Judgment

Keira Bell: The High Court hands down a historic judgment to protect vulnerable children

An analysis of the court judgment and what it reveals about the Tavistock by lawyer Naomi Cunningham

Puberty blockers and parental consent