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Puberty Blockers are not reversible

Updated: Nov 7, 2023

Puberty blockers lead to irreversible serious side effects

and are poorly researched.

It is stated by trans activists and those who administer Puberty Blockers (PBs), that they are essentially harmless, fully reversible, and free of any serious side effects. They are promoted as a good way of delaying or stopping the onset of puberty, so that the young person with gender dysphoria (GD) may not experience the physical changes of the sex they do not want, and that they can have time to think about transition. They are then frequently given from the age of 12, or even younger. We need to look at the facts.

Major Irreversible Side effects

Brain development

The brain is not fully mature until around the age of 25. The sex hormones, testosterone or oestrogen, that are being blocked by PBs, are essential for normal brain growth (Goddings et al. 2013). The brain has specific receptors for these hormones and puberty is a key stage in the maturation of the brain. By removing the normal physiological processes involved, we are putting young people at risk of abnormal brain development. A recent trial of using PBs in monkeys (Godfrey et al, 2023) demonstrated that, compared to controls, the brains of those who had PBs had broad and profound delay in brain development.

Bone density

It has been clearly demonstrated that those who take PBs have significant reduction in expected bone density by the age of 22 (Klink et al, 2015). Some have density at the level of osteoporosis. The risk of fractures and permanent disability from this is very real.


Over 95% of those who are prescribed PBs go on to cross-sex hormone treatment as well, by the age of 16 (Carmichael et al, 2021). This is because, once on the medical trajectory, it is very hard for the young person to change course. Sex hormones are essential for normal development of ovaries and testes. Infertility is therefore very common if cross sex hormones are used as well as PBs (Gender dysphoria treatment, website). Such infertility is irreversible. Starting on PBs therefore leads to infertility.

Sexual function

By taking PBs the sexual organs fail to develop normally. This is compounded by the almost inevitable addition of cross sex hormones. Many of those who have gone through this process have abnormal sexual function with inability to achieve orgasm.

Body growth

Puberty is essential for increased growth velocity at a critical period, a normal physiological process. Blocking puberty leads to reduced height (Carmichael et al, 2021).

Given all these serious and irreversible effects, how can a 12 year-old child give informed consent to such treatment?

Effect on desistance

Good research shows that if left without PBs around 80% of children will desist from their GD (Steensma et all, 2013., Singh et al, 2021). Desistance occurs when the child is older, and feelings of dysphoria go away. By avoiding the normal processes of puberty with PBs, a child will not experience the hormonal influences that lead to maturity and sexual development. PBs combined with an environment of affirmation of the GD, is likely to inhibit any desistance. This effect of PBs on preventing desistance is reflected in the fact that over 95% of those on PBs go on to have cross-sex hormones, and often surgery.

Flawed research on puberty blockers

The protocols for PBs in our gender clinics are based on Dutch studies earlier this century. A key one is that of de Vriess et al. (2014) of 70 individuals. It was reported that in the short term there was improvement in depression in the children given PBs. This study was flawed in many ways: long-term outcomes were not known, outcomes were measured in only 55 individuals (omitting non-completers), of those 15 not included 3 developed side effects causing them to stop, 2 refused to continue and 1 died from sepsis after genital surgery. This study is still held up in Scotland as foundational for the use of PBs (known as the ‘Dutch Protocol).

As for improvement in either the GD or mental health in those taking PBs; no improvement was found in the only research published by NHS England children’s clinic -Tavistock GIDS (Carmichael et al, 2021). In fact, careful study of that research shows that a significant number of those taking PBs had worse mental health.

Currently, the Sandyford NHS clinic in Glasgow prescribes PBs to many young children with GD. This is despite the Cass review in England showing such treatment to be unsafe. It is alarming that an un-scientific ideology of affirmation and medicalisation is causing such harm to young people.

Authored by Dr Antony Latham, Retired GP, and Chair of the Scottish Council on Human Bioethics


Carmichael P., Butler G., Masic U., Cole T., De Stavola B., Davidson S., Skakeberg E., Khadr S. and Viner R. (2021) ‘Short-term outcomes of pubertal suppression in a selected cohort of 12 to 15 year old young people with persistent gender dysphoria in the UK’ Plos one pp 1-26

De Vries, A., McGuire, J., Steensma, T., Wagenaar, E., Doreleijers, T. and Cohen-Kettenis, P. (2014) ‘Young Adult Psychological Outcome after Puberty Suppression and Gender Reassignment.’ Pediatrics 134 (4) pp. 696-704

Goddings, A., Mills, K., Clasen, L., Viner, R. and Blakemore, S. (2013) ‘The influence of puberty on subcortical brain development.’ NeuroImage 88 pp. 242-251

Godfrey, J.R., Howell, B.R., Mummert, A., Shi, Y., Styner, M., Wilson, K.E. and Sanchez, M. (2023) ‘Effects of social rank and pubertal delay on brain structures in female rhesus macaques.’ Psychoneuroendocrinology 149, 105987

Klink, D., Caris, M., Heijboer, A., van Trotsenburg, M, and Rotteveel J., (2015) ‘Bone mass in young adulthood following gonadotropin-releasing hormone analog treatment and cross-sex hormone treatment in adolescents with gender dysphoria.’ Journal of Clinical Endocrinology & Metabolism 100 (2) pp. 270-275

Singh, D. et al., (2021) ‘A Follow-Up study of Boys with Gender identity disorder.’ Front. Psychiatry 12

Steensma, T., Mcguire, J., Kreukels, B., Beekman, A. and Cohen-Kettenis, P., (2013) ‘Factors Associated with Desistance and Persistance of Childhood Gender Dysphoria: A Quantitative Follow-up Study’ Journal of the American Academy of Child and Adolescent Psychiatry 52 (6), pp. 582-590

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