How hormone blockers put puberty on pause

Hormone therapies are medications with a variety of uses — from birth control, to treating symptoms of menopause, to fighting prostate cancer. But lately, one use in particular has been at the centre of a growing political storm: blocking puberty.

When used as a puberty blocker, hormone therapy delays the sexual development changes of puberty.

Puberty blockers have become a contentious issue in Canada, the U.S. and Europe, as politicians debate the use of these medications in children of various ages. Their use has been banned for minors in several U.S. states, and Alberta Premier Danielle Smith recently announced her government plans to introduce similar policies.

Here's a closer look at how puberty blockers are used in medicine.

When are puberty blockers prescribed?

Puberty blockers were originally used for precocious puberty, which is when a child's body starts to take on adult characteristics — such as breast development or pubic hair — before the age of eight for girls or nine for boys.

Doctors also prescribe puberty blockers to adolescents with gender incongruence or dysphoria — lasting distress due to a mismatch between one's sense of their own gender and their biological sex assigned at birth — in order to pause puberty and give them more time to explore their options.

"The clinical objective of prescribing a hormone blocker is to provide a young person with time to further explore their gender identity without pressure or distress related to ongoing development of secondary sex characteristics," or gendered experiences such as menstruation or erections, the Canadian Paediatric Society says in its 2023 position statement on affirming care for transgender and gender-diverse youth.

It adds that hormone blockers should not be prescribed before a child begins puberty.

Before an adolescent can consent to treatment, mental health providers confirm their understanding of the pros and cons of treatment and how puberty will resume if they stop taking the blockers.

Dr. Jake Donaldson, a primary care physician at Pinnacle Medical Centres in Calgary, consults on 2SLGBTQ+ care, including hormone replacement therapy for transgender and gender non-binary individuals.

He says when puberty blockers are given too late in the process of puberty, some changes to the body become permanent and might need surgery to reverse.

"The critical time for puberty blockers is the onset of puberty," Donaldson said in an interview with CBC's Canada Tonight. "If you introduce it after that, it's too late."

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How do puberty blockers work?

A common type of puberty blocker is gonadotropin-releasing hormone (GnRH) analogues. These are chemical compounds similar in structure to the hormone made and released by a gland in the brain.

The medications stop receptors in the brain from producing sex hormones, which pauses puberty.

GnRH analogues are typically given as injections every one to three months.

How safe are puberty blockers?

Since puberty blockers only pause puberty, the physical changes aren't permanent.

"Risks of puberty blockers are actually very low," Donaldson said.

Earlier studies suggested that when children are on puberty blockers, their bone density doesn't keep up with that of their peers. But more recent research found they eventually caught up once they started hormone therapy, he added.

Robyn Hodgson, a registered nurse with the Trans Health Team at the London InterCommunity Health Centre, said health-care providers can also offset the minor risk of underdeveloped bones by prescribing calcium and vitamin D supplements.

Adolescents with gender dysphoria also face risks when they do not receive puberty blockers, particularly when it comes to their mental health.

"When young people are growing up in a body that does not reflect who they are, [it] puts them at severe risk for self harm, whether that's cutting, whether that's excessive drug or alcohol use or risky behaviours, and that further puts them at risk for suicide," said Dr. James Makokis, a two-spirit family physician who provides gender-affirming care in Edmonton.

Another consideration for adolescents is whether they wish to have biological children in the future. The Canadian Paediatric Society recommends discussing fertility before they start taking puberty blockers.

Dr. Daniel Metzger, a pediatric endocrinologist at B.C. Children's Hospital, said transgender boys who have already started menstruating are typically given the birth control pill or an intrauterine device (IUD) instead of blockers. Older trans girls can store their sperm for later use before they start using hormone therapy, he said.

What about hormone treatments?

Some trans youth may decide to pursue gender-affirming hormone therapy (GAHT), in which they receive hormones — estrogen for women, testosterone for men — that help them develop sex characteristics aligned with their identity.

Before they can begin treatment, they are often required to meet with psychiatrists, pediatricians or other medical professionals for a series of assessments — for example, making sure they understand the risks and benefits or the medications, and that any psychological or medical issues that could interfere with treatment have been addressed.

Pediatricians say GAHT has some irreversible effects, such as a deeper voice for those who take testosterone and breast development for those who take estradiol, a form of estrogen.

"As someone is coming to greater emotional, mental maturity, if they continue to struggle with their gender identity, then we can start looking at what some of those hormonal options might be," said Hodgson.

But she added that she's also seen people who "decided that they were quite comfortable" with puberty blockers alone and chose not to proceed with GAHT.

In a recent two-year study of transgender and non-binary youth in the U.S., participants who received GAHT reported improved satisfaction with their lives, less anxiety and depression, and better alignment between their gender identity and physical appearance.

However, an editorial accompanying the study in the New England Journal of Medicine cautioned that while results were positive overall, some individual participants still reported depression or anxiety after two years or GAHT. It noted that the study didn't account for other supports that could have affected participants' psychological outlook, such as mental health care.

The editorial concluded that more study is needed and suggested looking at different care models to get a better idea of which ones had the best chance of supporting youth receiving GAHT.

If you or someone you know is struggling, here's where to get help:

• Suicide Crisis Helpline: Call or text 988.

• Kids Help Phone: 1-800-668-6868 (phone), live chat counselling on the website.

• Canadian Association for Suicide Prevention: Find a 24-hour crisis centre.

• This guide from the Centre for Addiction and Mental Health outlines how to talk about suicide with someone you're worried about.