Objective: To analyze the effectiveness and safety of growth hormone (GH) replacement treatment in adult patients with Langerhans cell histiocytosis (LCH) and GH deficiency (GHD) enrolled in KIMS (Pfizer International Metabolic Database). Patients and methods: Patients with LCH and GHD were studied at baseline and some of them after 1 year of GH treatment. The effectiveness of GH is presented as change after 1 year of treatment (mean, 95% CI). The LCH population was compared to two other groups of patients enrolled in KIMS, granulomatous and lymphocytic hypophysitis. Results: At baseline, 81 adults with LCH (27 with childhood onset, 56% females), mean age at GHD onset of 29 (15) years were studied. Diabetes insipidus was diagnosed in 86% of patients. Analysis of 1 year of GH treatment was possible in 37 patients. One-year cross-sectional values for the GH dose were 0.39 (S.D. ± 0.21) mg and -0.5 (-1.2 to 0.2) for insulin-like growth factor-1 S.D. Total cholesterol decreased 0.9 (-1.5 to -0.3 (mmol/L); P < 0.05); AGHDA-QoLscore (n = 20) was improved by 2.8 points (-5.6 to 0.0; P < 0.05), while mean BMI increased 0.6 ± 3 kg/m2 (95% CI: -0.2 to 1.4). All these effects did not differ from the two other groups after adjusting for age, gender, and baseline values. In 20 of 77 patients included in the safety analysis, 36 serious adverse events were reported during 435 patient-years (82.8/1000); no new safety signals were reported. Conclusion: After 1 year of GH treatment in patients with LCH, metabolic variables and quality of life improved, with no new safety signals.