What Are Puberty Blockers?

How do they work?

Typically, in puberty, gonadotropin-releasing hormone helps to produce follicle-stimulating hormone (FSH) and luteinizing hormone (L.H.). In people assigned female at birth, these hormones prompt the ovaries to make estrogen, which promotes processes like breast growth and menstruation. In people assigned male at birth, they prompt the testes to make testosterone, which promotes processes like facial hair growth and a deepening of the voice.

Puberty blockers disrupt the production of FSH and L.H., therefore blocking the production of estrogen or testosterone. As a result, transgender adolescents do not continue to develop unwanted secondary sexual characteristics — transgender boys do not develop breasts and transgender girls do not develop facial hair, for example.

Puberty blockers do not stop an early stage in sexual maturation called adrenarche, which can cause acne, the growth of underarm and pubic hair and body odor.

Who can get puberty blockers?

Although parents might think they should start puberty blockers very young, so that a child never has to experience any physical changes associated with the unwanted gender, experts say it’s better to wait at least until the early stages of puberty have started. Dr. Stephen Rosenthal, medical director of the child and adolescent gender center for U.C.S.F. Benioff Children’s Hospitals, was a co-author of the Endocrine Society’s 2017 guidelines for transgender health care. He recommended starting puberty blockers when breast budding or the enlargement of the testes has begun, at the earliest.

That’s because Dr. Rosenthal does not recommend puberty blockers for prolonged use outside of the normal window of puberty. They restrict the functioning of the gonads, which may lead to adverse health effects. The longer blockers are used past the typical start of puberty — generally age 14, at the latest — the greater the possible risk.

When blockers are initiated in the early stages of puberty, Dr. Rosenthal typically suggests that his patients stop using them by age 14. At that point, patients, with their families and their doctors, can determine whether to introduce hormones that help them develop according to their gender identity or resume puberty in the gender assigned at birth.

Dr. Rosenthal further recommended that before starting blockers, children be evaluated by a mental health professional and determined to have gender dysphoria. He said families should also undergo a thorough process of informed consent, during which they are educated about the potential effects of blocking puberty — including adverse ones.