124 Chapter 7 ABSTRACT Purpose: Treatment for transgender adolescents with puberty suppression (PS) was developed to provide time for exploration before pursuing gender-affirming medical treatment (GAMT) with irreversible effects. It may also result in a more satisfactory physical outcome for those who continue with GAMT. Despite being the current first choice treatment, little research has examined the function of PS from the perspectives of transgender adolescents, their parents, and clinicians. Insight into the perceived functions of PS will help to adequately support adolescents in their decision-making process and give them the care they need. Methods: Qualitative study using interviews with eight transgender adolescents who proceeded with GAMT after PS (‘continuers’), six adolescents who discontinued PS (‘discontinuers’) and 12 parents, and focus groups with ten clinicians. Results: All informants considered inhibition of development of secondary sex characteristics an important function of PS. Most continuers saw PS as the first step of GAMT. Nevertheless, some were glad that the effects were reversible even if they did not expect to change their minds. Some discontinuers did experience PS as an expanded diagnostic phase. One continuer used the time on PS to get used to living in the affirmed gender role, and several parents found the time helpful to adapt to their child’s new gender role. PS provided clinicians more time for diagnostic assessment. Conclusions: Adolescents, parents and clinicians do not all report the same functions of PS. Although international guidelines emphasize providing time for exploration of gender identity as an important reason for PS, many adolescents nowadays seem to have clear ideas about their gender identity and treatment wishes, and experience PS as the first step of GAMT. For some discontinuers however, PS offered a valued period of exploration. Guidelines could be modified to provide more customized care, taking adolescents’ and parents’ ideas about the functions of PS into account.