Background/Aim: This longitudinal study aimed to analyze the prevalence of endocrine disorders in childhood brain tumor survivors in South Korea using claims data. Patients and Methods: We identified in 1,058 patients from a nationwide cohort of patients diagnosed with brain tumors between January 1st 2009 to March 29th 2016. Multivariable logistic regression was used to evaluate associations between clinical factors and endocrine disorders. Results: After a median follow-up of 60.0 months, 393 (37.1%) patients had at least 1 endocrine disorder. The commonest endocrine disorders were hypopituitarism (17.4%) and hypothyroidism (6.1%). Female gender (odds ratio(OR)=1.45, p=0.005) and age <10 years (OR=1.65, p=0.001) conferred a higher risk. Patients who received radiotherapy were more likely to have endocrine disorders compared to those who did not (OR=1.79, p<0.001). Conclusion: Regular assessment of endocrine function and timely interventions are necessary for childhood brain tumor survivors with a risk of endocrine disorders. Brain tumors are the second commonest cause of cancer in children and account for 21% of all pediatric cancers (1). Advancements in treatment have allowed 74% of children diagnosed with brain tumors to become long-term survivors (2). Despite improvements in prognosis, cancer survivors continue to suffer from treatment-related side-effects that impair their quality of life (3). These adverse effects may be related to the tumor burden, surgical interventions, chemotherapy, or radiotherapy (4). Many of the late effects are attributable to direct damage of brain development (5), and include disorders of the endocrine system (6). Among them, childhood brain tumors located near the hypothalamic-pituitary area are particularly associated with an increased risk of hypothalamic pituitary axis (HPA) dysfunction (7). Common endocrine complications include the growth hormone (GH) deficiency and insufficient levels of thyrotropic and adrenocorticotropic hormones (8). In addition, the prevalence of endocrine disease among patients with childhood brain tumors is 49%, and that of more than one endocrine deficiency is estimated to be 40% (9). Reports suggest that the lack of an appropriate and timely follow-up escaping diagnosis of developing endocrine disorders could result in late referrals, adversely affecting the hormone balance of these patients (10). Reports on the number of childhood brain tumor survivors being currently treated for endocrine disorders in South Korea are scarce. In addition, recommendations for screening endocrinopathy are based on limited variables and as a result of studies in small patient populations (11). For all these reasons, we aimed to analyze large-scale nationwide data for identifying the prevalence of endocrine disorders among childhood brain tumor survivors. We also evaluated the risk factors associated with these disorders. Patients and Methods Patients under 18 years of age who were diagnosed with pediatric brain tumors between January 2007 and December 2016 were ident...