Puberty blockers, puberty inhibitors, or hormone blockers are hormonal therapies used to delay the onset of puberty in children. The most commonly used puberty blockers are gonadotropin-releasing hormone agonists, which suppress the production of sex hormones (gonadotropins) like testosterone and estrogen. If the child receiving puberty blockers wishes to commit to a gender transition, the next step would be to begin hormone therapy.
Puberty blockers are drugs which are used to prevent the natural progression of puberty in children at least 12 years of age and adolescents by blocking sex hormone production. These drugs are given to children and adolescents who seek to identify as opposite to their biological sex. For example, a female child who wishes to identify as a male would take hormone blockers to prevent the growth of breasts and ovary development by blocking the production of sex hormones. Puberty blockers are often marketed to misguided (or malevolent) parents of prepubescent children who claim to 'identify' as transsexual or transgender. Despite the fact that activists often falsely claim the effects of puberty blockers are reversable, disruption of puberty in children and adolescents leaves them underdeveloped later in life. When used consistently, the effects of puberty blockers are irreversible. Even if the drugs are used and treatment is halted around the mid to late teens (15-18), a recipent will be left with irreversible damage to their reproductive organs and body.
The numerous side effects of puberty blockers are problematic for post-pubescent persons who seek to either live as their biological sex or undergo bottom surgery. The drugs can result in mishandled or botched surgeries. Puberty blockers are also suspected to be carcinogenic, but research confirming this has not yet been published.
Malvina Skorska, a researcher at the Canadian Institute of Health Research, writes in a 2020 grant proposal that "Surprisingly, even though puberty blockers are widely used to help transgender adolescents go through gender transition, their impact on brain function during this critical stage of brain development is largely unknown."
https://blogs.bmj.com/bmjebmspotlight/2019/02/25/gender-affirming-hormone-in-children-and-adolescents-evidence-review/#:~:text=Guidelines require puberty to have,young as 12 years old.
 Rew L, Young CC, Monge M, Bogucka R. Review: Puberty blockers for transgender and gender diverse youth-a critical review of the literature. Child Adolesc Ment Health. 26 Feb. 2022 (1):3-14. doi: 10.1111/camh.12437. Epub 2020 Dec 15. PMID: 33320999. https://pubmed.ncbi.nlm.nih.gov/33320999/
 Shrier, Abigail. Irreversible Damage. Regnery Publishing, 2020.
 Skorska, Malvina Nina, et al. “Effects of Puberty Blockers on Brain Function in Adolescents Experiencing Gender Dysphoria: A Functional Magnetic Resonance Imaging Study.” Dimensions, Canadian Institutes of Health Research (CIHR), 1 Jan. 2020, https://app.dimensions.ai/details/grant/grant.8675580.