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Expert Statements on Puberty Blockers


The Ministry of Health describes puberty blockers as "safe and fully reversible" on their website

We have written to the Ministry informing them of the lack of evidence for this statement and asked for its removal. The Ministry responded that the statement "remains appropriate". The Ministry has abandoned their responsibility to provide accurate medical information.

The sections below collate expert statements on puberty blockers that contradict the "safe and fully reversible" claim.


Impacts on Cognitive Function#


Autistic girls seeking answers ‘are seizing on sex change’ [link]#


"...puberty blockers have profound effects on the developing body, and as part of the changes seen in adolescence involve hormonal effects on brain function, the impact of these drugs on the brain maturation are likely to be deleterious"

Professor Sophie Scott, director of the Institute for Cognitive Neuroscience, University College London, UK


"IQ might be damaged by puberty blockers."

Professor Christopher Gillberg, Child and Adolescent Psychiatry at Gothenburg University in Gothenburg, Sweden



Use of puberty blockers for gender dysphoria: a momentous step in the dark [link]#


"...[puberty blockers are] likely to threaten the maturation of the adolescent mind."

Dr Christopher Richards - Paediatrician, Newcastle upon Tyne, UK

— Dr Julie Maxwell - Paediatrician, Hampshire, UK

— Dr Noel McCune - Psychiatrist (retired), Child and Adolescent Mental Health Service, Portadown, Northern Ireland, UK



Growing Pains [link]#


"...there are reasons to suspect that [puberty suppression] could have negative consequences for neurological development."

Associate Professor Paul Hruz - Paediatrics and Endocrinology, Washington University School of Medicine, St. Louis, USA.

Professor Lawrence S Mayer - Psychiatry, Johns Hopkins University School of Medicine and Statistics and Biostatistics, Arizona State University, USA.

Professor Paul R. McHugh - Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, USA.



Hayes, 2017 [link]#


"the research has, in fact, reinforced concerns over the impact of GnRHas on cognitive performance in children."

"Any findings which indicate that GnRHas cause a decline, even a modest decline, in IQ are likely to be of considerable interest to patients and their parents. It is a factor that they may well want to consider in deciding whether or not to take the drug."

Dr Peter Hayes - Faculty of Education and Society, University of Sunderland, Sunderland, UK



Hough et al, 2017#


"...some cognitive functions may be irreversibly altered by [puberty supression]"

"[puberty suppression] may also have long lasting effects on other brain areas and/or aspects of cognitive function."

"deficits in long-term spatial reference memory...are likely permanently altered"

"The observation that [puberty suppression] is associated with permanent changes in brain development raises particular concerns about the cognitive changes associated with the prolonged use of GnRHa-treatment in children and adolescents."

Dr Denise Hough - Lecturer in Biology, University of Glasgow.

Dr Michelle Bellingham - Lecturer in Comparative Physiology, University of Glasgow.

Dr Irah Haraldsen - Head of Cognitive Health in Brain Disorders Group, University of Oslo.

Dr Mark McLaughlin - Senior Lecturer in Vetinary Science and Education, University of Glasgow.

Dr Jane Robinson - College of Medical, Vetinary and Life Sciences, University of Glasgow.

Associate Professor Anne-Kristin Solbakk - Department of Psychology, University of Oslo.

Professor Neil Evans - Institute of Biodiversity, Animal Health & Comparative Medicine, University of Glasgow.



Schneider et al, 2017#


The patient's GIQ (global IQ) was further slightly reduced during the follow-up with GnRHa treatment. In fact, the low average GIQ together with impairment in the perceptual organization of intelligence and processing speed index presented even before treatment...suggest that any neurodevelopmental immaturity may have been potentiated by pubertal suppression.

Some questions emerge from these findings, especially regarding the influence of sex steroids on cognition during puberty. It is likely that the structural and microstructural changes in the brain during adolescence, as discussed above, may interfere on the achievement of complete cognitive potential.

Assistant Professor Maiko Schneider - Psychiatry and Behavioural Neurosciences, McMaster University, Canada.

Professor Poli Spritzer - Physiology and Endocrinology, Universidade Federal do Rio Grande do Sul, Brazil

Bianca Machado Borba Soll - Doctoral Candidate in Psychiatry, Universidade Federal do Rio Grande do Sul, Brazil

Dr Anna M V Fontanari - Gender Identity Program, Universidade Federal do Rio Grande do Sul, Brazil

Dr Fernanda Tovar-Moll - Director, Instituto D’Or de Pesquisa e Ensino, Rio de Janeiro, Porto Alegre, Brazil

Adjunct Professor Angelo B Costa - Psychology, Pontifical Catholic University of Rio Grande do Sul Porto Alegre, Brazil

Dr Dhiordan Cardoso da Silva - Psychiatry, Universidade Federal do Rio Grande do Sul, Brazil

Dr Karine Schwarz - Instituto da Voz, Universidade Federal do Rio Grande do Sul, Brazil

Dr Silza Tramontina - Child and Adolescent Psychiatry Service, Hospital de Clínicas de Porto Alegre, Porto Alegre, Brazil

Dr Maria I R Lobato - Psychiatry and Forensic Medicine Service, Hospital de Clínicas de Porto Alegre, Porto Alegre, Brazil



Safety and Reversibility#


Karolinska Hospital [link]#


"[Puberty blockers and cross-sex hormones] are potentially fraught with extensive and irreversible adverse consequences such as cardiovascular disease, osteoporosis, infertility, increased cancer risk, and thrombosis. This makes it challenging to assess the risk/benefit for the individual patient, and even more challenging for the minors and their guardians to be in a position of an informed stance regarding these treatments."


Newstalk interview: Are Puberty Bockers Reversible? [link]#


"There is not enough evidence to say they’re reversible...We know that when you interrupt any process in the body...there are consequences...you can't say 'completely reversible'"

Professor Donal O'Shea - Endocrinologist, St Vincent's Private Hospital, Dublin, Ireland



Van Meter, 2020 [pdf]#

"To treat puberty as a pathology that should be prevented by administration of puberty blocking drugs is to interrupt a major and necessary physiologic transformation at a critical age when such changes can effectively happen. The physiologic event of puberty cannot safely be put off to a later date."

Adjunct Associate Professor Quentin L Van Meter - Pediatric Endocrinologist, Emory University, Georgia, USA.



Growing Pains [link]#


"The claim that puberty suppression for adolescents with gender dysphoria is “reversible” is based on speculation, not rigorous analysis of scientific data."

"Whether puberty suppression is safe and effective when used for gender dysphoria remains unclear and unsupported by rigorous scientific evidence."

"...whether blocking puberty is the best way to treat gender dysphoria in children remains far from settled and it should be considered not a prudent option with demonstrated effectiveness but a drastic and experimental measure."

Associate Professor Paul Hruz - Paediatrics and Endocrinology, Washington University School of Medicine, St. Louis, USA.

Professor Lawrence S Mayer - Psychiatry, Johns Hopkins University School of Medicine and Statistics and Biostatistics, Arizona State University, USA.

Professor Paul R. McHugh - Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, USA.



Experimenting on Gender Dysphoric Kids [link]#

"If [researchers]...had extended their search to the effect of blockers on the brains of adult humans as well as laboratory and animal work...they would have been rewarded with many references that would have warned them that the effects of blockers are not “safe” and “reversible”..."

Professor John Whitehall -Foundation Chair Paediatrics and Child Health, University of Western Sydney, Australia.



The Pediatric Endocrine Society’s Statement on Puberty Blockers Isn’t Just Deceptive. It’s Dangerous [link]#

What people don’t usually consider is that puberty is also extraordinarily important in female pelvic maturation, and in the normal bone structure and brain development of both sexes. Additionally, the physical changes of puberty occur in the wider context of complex developmental milestones as the child progresses toward social independence from his or her parents...Disruption of a temporal process of development cannot be reversed."

Dr Michael Laidlaw - Endocrinologist, California, USA.