Keira Bell case: What are puberty blockers?

An appeal hearing over a High Court decision which led to most under-16s being barred from accessing puberty blockers is taking place on Wednesday.

Puberty blockers are prescribed to some children who are experiencing gender dysphoria, to temporarily stop their bodies developing.

The NHS describes gender dysphoria as “a sense of unease that a person may have because of a mismatch between their biological sex and their gender identity”.

What do they do?

Puberty blockers suppress the release of hormones which start to be produced in much bigger quantities during puberty.

The hormones are messengers telling your body to develop things like breasts, periods, facial hair or a deeper voice.

The drugs are also used to treat conditions which cause premature puberty in much younger children.

“Higher prevalence of autistic spectrum conditions in clinically referred, gender dysphoric adolescents than in the general adolescent population.”

Why are they used?

The Gender Identity Development Service (Gids), based in London and Leeds, says that pausing puberty is designed to give a young person with gender dysphoria more time to consider their options – while not having to go through the additional distress of their body changing in a way they do not want.

When someone stops taking blockers, puberty should resume.

By pausing puberty, and the development of things like breasts or facial hair, someone who goes on to have cross-sex hormone therapy may avoid having more invasive surgical treatment like having their breasts removed (mastectomy) later on.


A counsellor talking to a mother and child (stock image)

image copyrightGetty Images

Cross-sex hormone therapy involves taking testosterone, a masculinising hormone, or oestrogen, a feminising hormone. It a treatment only available to over-16s on the NHS in England.

The NHS trusts involved in the appeal argue taking puberty blockers and cross-sex hormones are completely separate stages of treatment, though the limited evidence that exists suggests that most young people beginning the first treatment go on to the second.

Who is allowed to access puberty blockers?

The rules about who can give consent to use of puberty blockers have changed recently.

In 2020, three senior judges ruled that children under 16 are unlikely to be able to give informed consent to treatment involving puberty-blocking drugs.

As part of the ruling, they said “there is real uncertainty over the short and long-term consequences of the treatment with very limited evidence as to its efficacy, or indeed quite what it is seeking to achieve. This means it is, in our view, properly described as experimental treatment”.


Keira Bell


One of the claimants, Keira Bell, was prescribed puberty blockers aged 16. She later changed her mind over her decision to transition to a male, and stopped taking the hormones. She has argued the gender identity clinic should have challenged her more in her original decisions to transition.

The Tavistock and Portman NHS Trust, which runs the clinic, is now challenging the decision in the Court of Appeal.

In a separate ruling in March 2021, the Family Division of the High Court ruled parents can consent to the treatment on behalf of their child, although additional safeguards should be considered.

NHS England subsequently announced that it would set up a review group to assess the prescription of puberty blockers for under-16s.

It’s also awaiting the outcome of an independent review into gender identity services for children, which it said will inform its longer term approach.

The NHS says when children are referred to the gender identity service they will be seen by a team of professionals, including psychologists, therapists and social workers. Most of the treatments offered at this stage will be psychological rather than medical, with puberty blockers only given to those who meet “strict criteria”.

Why are puberty blockers controversial?

The court cases have centred on whether under-16s can “understand and weigh the long-term risks and consequences” of taking puberty blockers.

Puberty hormones are linked to changes not just in the body but also in the brain.

Some early data from one study showed some of those taking the drugs reported an increase in thoughts of suicide and self-harm, but it was unable to say whether it was the drugs or something else causing the increase.

Experts on clinical trials criticised the design of the study, but said the data warranted further investigation.

Children with gender dysphoria not taking puberty blockers are thought to experience increases in suicidal thoughts over time.

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

“Although 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”.

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The National Institute for Health and Care Excellence (NICE) lists a decrease in bone density as a possible side effect of triptorelin, the puberty blocker drug used by Gids.

It has also been claimed puberty blockers may effect someone’s fertility and sexual functioning, but evidence around this is also limited.

The other claimant on Keira Bell’s court case, known as Mrs A, is the mother of a teenager with autism who was on the waiting list for treatment.

Gids says that there seems to be a “higher prevalence of autistic spectrum conditions in clinically referred, gender dysphoric adolescents than in the general adolescent population”.

The judges said their original decision was only on the informed consent of a child or a young person, not whether puberty blockers were appropriate themselves.

Has there been an increase in referrals?

There was a large increase in children being referred to Gids between 2014 and 2018, which has levelled off more recently.

Gender Identity Development Service annual referrals. . .

While there is no clear explanation for what prompted the increase in referrals, Gids puts it down to greater awareness.

Large increases in referrals have also been seen at gender identity clinics elsewhere, for example in the US and Canada.

There has also been a shift in the past few years, with people whose sex at birth is female making up the bulk of the increase in young people wanting to transition.

Gids says its team are “are alive to this issue and are exploring it”.

Referrals by sex assigned at birth. . Includes referrals that were not accepted.

What is the prescribing process?

Puberty blockers, when used to treat gender dysphoria, can only be initially prescribed by a specialist, rather than a GP.

They are prescribed by the NHS to children or young people who have already started puberty. This process begins often years before any physical signs of puberty appear and has to be assessed by a hormone specialist.

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