We retrospectively studied 61 patients with GH deficiency (GHD), identified among 589 patients with Langerhans cell histiocytosis (LCH) enrolled in a nationwide survey between 1993 and 2001. Overall, 141 patients in the survey developed diabetes insipidus. The median follow-up of the 61 patients with GHD was 12 yr. The 5- and 10-yr risks of GHD among patients with diabetes insipidus were 34.7 +/- 4.5% and 53.7 +/- 5.2%, respectively. Growth velocity decreased soon after LCH diagnosis in patients who developed GHD, and anterior pituitary height, estimated by magnetic resonance imaging, was significantly reduced relative to patients who remained free of GHD. GH replacement therapy was administered to 47 of the 61 patients with GHD. Among GH-treated patients, median final height (-0.8 SD) was significantly greater than median height at GHD diagnosis (-1.6 SD) but remained below midparental (target) height. Among patients with pituitary involvement, the number of LCH disease episodes appeared not significantly influenced by GHD or GH administration, suggesting an absence of deleterious effect of GH therapy on LCH disease activity.