Inclusion and exclusion criteria
| Population | Children and/or adolescents aged 0–18 experiencing gender dysphoria, gender incongruence or referral to a gender identity service. Studies of adults or a mixed population of adolescents and adults where treatment was initiated in adolescence (<18). |
| Intervention | Masculinising or feminising hormone treatments. |
| Comparator | Any or none. |
| Outcomes | Pubertal development, side effects, gender dysphoria or other gender-related outcomes, psychological health, physical health, psychosocial outcomes, cognitive outcomes, fertility. |
| Study design | Clinical trials, cohort studies, case–control studies, cross-sectional studies, pre–post single-group design studies or service evaluations that provided treatment outcome data. Case studies and case series were excluded. |
| Publication | Studies published in the English language in a peer-reviewed journal. Conference abstracts were excluded. |