Supplementary Material for: Predictors of Insulin-Like Growth Factor-I Responses to Growth Hormone Replacement in Young Adults with Growth Hormone Deficiency

Background/Aims: Physiological growth hormone (GH) secretion and insulin-like growth factor-I (IGF-I) levels are greater in young compared to older adults. We evaluated IGF-I levels and predictors of IGF-I responses in young adults on GH replacement. Design: From the KIMS database, 310 young adults (age 15-26 years) with severe GH deficiency related to childhood-onset disease and commenced on ‘adult GH replacement' were identified. ‘IGF-I responses' were estimated from first-year increments in IGF-I standard deviation scores (SDS) and adjusted for GH dose. Body composition was assessed by bioimpedance in 143 patients. Results: IGF-I levels increased markedly from baseline to 1 year of replacement (-3.75 ± 1.94 vs. -1.36 ± 1.86 SDS, p 2); 0.52 (0.15), p = 0.0007] and BMI SDS [1.06 (0.25), p Conclusions: Low IGF-I levels in young adults on treatment may reflect suboptimal GH replacement. Identification of predictors for IGF-I responses could lead to a more appropriate replacement strategy. Association between IGF-I responses and lean body mass suggests that maintaining age-appropriate IGF-I levels is important during therapy.