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This information sheet summarisescurrent scientific knowledge onthe effects of puberty blockers fortransgender youth. It is based on aliterature review by a researcherin transgender health, with inputfrom clinicians and communityexperts in transgender health andwellbeing. Its purpose is to assistwhānau, families and healthprofessionals supportingtransgender* young people. CURRENT EVIDENCE ONCURRENT EVIDENCE ONPUBERTY BLOCKERSPUBERTY BLOCKERSThe scientific name for puberty blockers isGonadotropin-releasing hormone analogues (GnHa).Puberty blockers are used to pause the physical changes of puberty thatcause or may potentially lead to distress for transgender young people. Thisgives them time to consider their gender before making decisions aboutwhether to proceed with gender-affirming medical interventions, e.g.hormones, at a later date.what are puberty blockers?We use the term transgender to refer to anyone whose gender is different than the gender they were assigned at birth. This is intended to include takatāpui, non-binary, and gender fluid people, alongsideanyone who seeks gender-affirming care to express their gender, however they might choose to identify.

Puberty blockers are reversible (Panagiotakopoulos et al 2020,Hembree et al 2017). Young people can stop taking them at any timeand puberty will recommence. Puberty blockers can be used once a transgender young person reachesTanner stage 2 of puberty and would otherwise start to developsecondary sex characteristics. Puberty blockers may also be helpful foradolescents who are further into puberty (Tanner stage 3-5) but areexperiencing ongoing changes that are causing distress.

how long have pubertyblockers been used?Use of puberty blockers for transgender young peoplehas increased in recent years, likely due to socialchanges meaning these young people feel more able tocome forward for help (de Vries et al 2021). Puberty blockers have been used since the 1980s totreat precocious puberty in children and they havebeen used in clinical care for transgender youngpeople since the 1990s (de Vries et al 2021).

Studies have highlighted that many transgender adults whodid not have access to puberty blockers wish they could havehad puberty blockers in adolescence (Turban et al 2020).Allowing puberty to progress in transgender young peoplewho experience gender dysphoria is not a neutral act and mayhave lifelong harmful effects (de Vries et al 2021).While the effects of puberty blockers are reversible, someof the effects of going through puberty are not. Takingpuberty blockers allows young people to avoid developingsecondary sex characteristics such as breasts, facial hair,an Adam’s apple, body hair and voice changes, which arehard or sometimes impossible to reverse. what are the effects ofpuberty blockers?Puberty blockers can reduce or prevent the need for expensive hairremoval procedures and invasive surgeries when transgenderyoung people are older, such as facial feminisation and chestmasculinising surgeries.

Some young people choose to stop takingpuberty blockers, as it is the appropriatestep for their personal gender development.Others choose to progress to gender-affirming hormone therapy. Evidence showsthat taking blockers does not influencethe choice to subsequently takehormones (Nos et al 2022). Rigorous observational studies show that puberty blockers improve the mental health andwellbeing of transgender young people, lowering depression and suicidal ideation andincreasing quality of life (Tordoff et al 2022, Achille et 2020, Turban et al 2020, Ashley,Olsen-Kennedy et al 2023, van der Miesen et al 2020).

These young people did not stopaccessing gender-affirming medicalcare, but rather went on to takehormones (Brik et al 2020). what are the risks ofpuberty blockers? All medicines have risks and benefits.Qualified health professionalsexplain these risks and benefits totransgender young people and theirwhānau or family, to ensure informedconsent. The young person and theirwhānau or family can then decide,with the support of their clinicians,whether or not to start on pubertyblockers. Like many other areas of medicine, long-term follow-up studies mayhelp to better understand the impact of puberty blockers across the lifecourse. However, existing data, including from their long-term use forprecocious puberty, suggest that puberty blockers are as safe as otherroutine medical care (Ashley, Olsen-Kennedy et al 2023).Side effects of puberty blockers arevery rare in the short term. One studyshowed a very small number of youngpeople decided to stop taking pubertyblockers due to symptoms includingmigraine, nausea and hot flushes.

To optimise bone health,it is important to ensure adequate calcium intakeand encourage physical activity (Hembree et al2017). Vitamin D supplements should be given if ayoung person has risk factors for vitamin Ddeficiency, especially in winter. A review of several recent studies shows no significantchange in bone density among young people on blockers(Joseph et al 2019). Some studies suggest transgenderyoung people may already have lower bone density prior totaking blockers, due to lifestyle factorssuch as reduced physical activity compared to their peers(Ceolin et al 2023).To reduce any potential impact on bone health, young peopleshould not stay on puberty blockers for prolonged periods,unless they go on to take hormones alongside pubertyblockers. Bone densityis likely to increase whena young person ceases blockersor starts hormones (Hembree et al2017, Schagen et al 2020).

The use of puberty blockers has become themost widely accepted clinical approach tosupporting transgender young people inspecialised transgender clinics around theworld and is accepted best practice amongstspecialist clinicians.It forms part of the two main internationalguidelines in the field (Coleman et al 2022,Hembree et al 2017). It is also reflected in theguidelines of many countries, includingCanada (Canadian Pediatric Society 2023),Australia (Telfer et al 2020) and New Zealand(Oliphant et al 2018).what is the qualityof the evidence aboutpuberty blockers?Randomised-controlled trials (RCTs)would provide high quality evidence ofthe full risks and benefits of blockersin the short and long term. But RCTscannot be used for this purposebecause it would be unethical towithhold puberty blockers fromtransgender young people for thepurpose of research, when they are thecurrent best treatment and withholdingthem poses a risk of serious harm(Ashley, Olsen-Kennedy et al 2023).

The lack of RCTs means thatevidence on the effects ofblockers is scientificallyclassified as ‘low quality’.‘Low quality’ evidence iscommon for manypaediatric conditionswhere it would be unethicalto withhold treatment, e.g.medications to treat fever,so this is not specific topuberty blockers.On this basis, a recentanalysis concludes thatclinicians can confidentlyprescribe puberty blockerswhere appropriate, based onthe current scientific evidence(Ashley, Olsen-Kennedy et al2023). The lack of RCTs does not mean that theuse of puberty blockers is based oninsufficient evidence (Ashley, Olsen-Kennedy et al 2023). Well-designedobservational studies can and havebeen used to ground reliablerecommendations for clinical practiceand policymaking in healthcare fortransgender young people, without theneed for RCTs (Ashley, Olsen-Kennedyet al 2023).

where can I get moreinformation?This is one of a series of three information sheetsabout puberty blockers, compiled in Aotearoa NewZealand in August 2023 by a researcher intransgender health, with input from clinicians andcommunity experts in transgender health andwellbeing. These information sheets can be downloaded atwww.projectvillageaotearoa.com/pubertyblockersText: Julia de Bres Graphic design: Ia Morrison-YoungIllustrations: Julia de Bres

references Achille C, Taggart T, Eaton NR, Osipoff J, Tafuri K, Lane A, & Wilson TA 2020. Longitudinal impactof gender-affirming endocrine intervention on the mental health and well-being of transgenderyouths: preliminary results. International Journal of Pediatric Endocrinology 8,https://doi.org/10.1186/s13633-020-00078-2Ashley F, Tordoff DM, Olson-Kennedy J, & Restar AJ 2023. Randomized-controlled trials aremethodologically inappropriate in adolescent transgender healthcare, International Journal ofTransgender Health, https://doi.org/10.1080/26895269.2023.2218357Brik T, Vrouenraets L J J J, de Vries MC, & Hannema SE 2020. Trajectories of Adolescents Treatedwith Gonadotropin-Releasing Hormone Analogues for Gender Dysphoria. Archives of SexualBehavior, https://doi.org/10.1007/s10508-020-01660-8.Canadian Pediatric Society 2023. Position statement: An affirming approach to caring fortransgender and gender-diverse youth. https://cps.ca/en/documents/position/an-affirming-approach-to-caring-for-transgender-and-gender-diverse-youthCeolin C, Scala A, Dall’Agnol M, Ziliotto, Delbarba A, Facondo P, Citron A, Vescovi B, Pasqualini S,Giannini S, Camozzi V, Cappelli C, Bertocco A, De Rui M, Coin A, Sergi G, Ferlin A, & Garolla A, onbehalf of the Gender Incongruence Interdisciplinary Group (GIIG) 2023. Bone health and bodycomposition in transgender adults before gender-affirming hormonal therapy: data from theCOMET study. Journal of Endocrinological Investment, https://doi.org/10.1007/s40618-023-02156-7Coleman, E., Radix, A. E., Bouman, W.P., Brown, G.R., de Vries, A. L. C., Deutsch, M. B., Ettner, R.,Fraser, L., Goodman, M., Green, J., Hancock, A. B., Johnson, T. W., Karasic, D. H., Knudson, G. A.,Leibowitz, S. F., Meyer-Bahlburg, H. F.L., Monstrey, S. J., Motmans, J., Nahata, L., ... Arcelus, J. 2022.Standards of Care for the Health of Transgender and Gender Diverse People, Version 8.International Journal of Transgender Health, 23(S1), S1-S260,https://doi.org/10.1080/26895269.2022.2100644

references de Vries, ALC, Richards C, Tishelman AC, Motmans J, Hannema SE, Green J, & Rosenthal SM 2021.Bell v Tavistock and Portman NHS Foundation Trust [2020] EWHC 3274: Weighing currentknowledge and uncertainties in decisions about gender-related treatment for transgenderadolescents. International Journal of Transgender Health 22:3, 217-224,https://doi.org/10.1080/26895269.2021.1904330Hembree WC, Cohen-Kettenis PT, Gooren L, Hannema SE, Meyer WJ, Murad MH, Rosenthal SM, SaferJD, Tangpricha V, & T’Sjoen GG 2017. Endocrine treatment of gender- dysphoric/gender-incongruent persons: an endocrine society clinical practice guideline. The Journal of ClinicalEndocrinology & Metabolism 102(11): 3869-903, https://doi.org/10.4158/1934-2403-23.12.1437 Joseph T, Ting J, & Butler G 2019. The effect of GnRH analogue treatment on bone mineral densityin young adolescents with gender dysphoria: findings from a large national cohort. Journal ofPediatric Endocrinology and Metabolism Oct 25;32(10):1077-1081, https://doi.org/10.1515/jpem-2019-0046Nos AL, Klein DA, Adirim TA, Schvey NA, Hisle-Gorman E, Susi A, & Roberts CM 2022. Associationof Gonadotropin-Releasing Hormone Analogue Use With Subsequent Use of Gender-AffirmingHormones Among Transgender Adolescents. JAMA Network Open 5(11):e2239758,http://doi:10.1001/jamanetworkopen.2022.39758Oliphant J, Veale J, Macdonald J, Carroll R, Johnson R, Harte M, Stephenson C, Bullock J, Cole D, &Manning P 2018. Guidelines for gender affirming healthcare for gender diverse and transgenderchildren, young people and adults in Aotearoa, New Zealand. NZMJ, 14 December 2018, vol 131, no1487.

references Panagiotakopoulos L, Chulani V, Koyama A, Childress K, Forcier M, Grimsby G, & Greenberg K2020. The effect of early puberty suppression on treatment options and outcomes in transgenderpatients. Nature Reviews. Urology, 17(11), 626–636, https://doi.org/10.1038/s41585-020-0372-2 Schagen, SEE, Wouters FM, Cohen-Kettenis PT, Gooren LJ, & Hannema SE 2020. Bone Developmentin Transgender Adolescents Treated With GnRH Analogues and Subsequent Gender-AffirmingHormones. Journal of Clinical Endocrinology and Metabolism Dec 1;105(12):e4252–63,https://doi.org/10.1210/clinem/dgaa604 Telfer MM, Tollit MA, Pace CC, & Pang KC 2020. Australian Standards of Care and TreatmentGuidelines for Trans and Gender Diverse Children and Adolescents Version 1.3.Melbourne: TheRoyal Children’s Hospital.Tordoff DM, Wanta JW, Collin A, Stepney C, Inwards-Breland DJ & Ahrens K. Mental HealthOutcomes in Transgender and Nonbinary Youths Receiving Gender-Affirming Care 2022. JAMANetw Open 5(2):e220978, doi:10.1001/jamanetworkopen.2022.0978Turban JL, King D, Carswell JM, & Keuroghlian AS 2020. Pubertal Suppression for TransgenderYouth and Risk of Suicidal Ideation. Pediatrics. 2020;145(2), https://doi.org/10.1542/peds.2019-1725Van der Miesen AIR, Steesnma TD, & de Vries ALC 2020. Psychological Functioning in TransgenderAdolescents Before and After Gender-Affirmative Care Compared With Cisgender GeneralPopulation Peers. Journal of Adolescent Health 66, 6: 699-704,https://doi.org/10.1016/j.jadohealth.2019.12.01