Reference Curve for the First-Year Growth Response to Growth Hormone Treatment in Prepubertal Children with Idiopathic Growth Hormone Deficiency: Validation of the KIGS First-Year Growth Response Curve Using the Belgian Register for the Study of Growth and Puberty Problems

Abstract

Background: Comparing observed and expected growth after first-year growth hormone (GH) therapy is useful for identifying a poor growth response to GH. Aim: To generate a first-year, age-specific growth response reference curve for prepubertal Belgian children with idiopathic growth hormone deficiency (iGHD) treated with a standard weight-adjusted GH dose and to compare this national reference with the response references derived from KIGS. Subjects and Methods: First-year height data of 357 prepubertal children (240 males) with iGHD were analyzed. Smooth reference curves of first-year height velocity (HV) in relation to age were created. Differences with the KIGS targets were evaluated after z-score transformation. Results: The observed first-year HVs were log-normal distributed by age and decreased significantly with age (p < 0.001). No GH dose or gender effect was observed (p = 0.5). Distance to target height, severity of GHD and occurrence of multiple pituitary hormone deficiencies had a positive effect (p < 0.01) on the calculated HV SDS. When applying the KIGS targets for severe iGHD, mean HV SDS was close to zero (-0.09 ± 0.84). Conclusion: The developed age-specific growth response curves enable rapid identification of poor response to first-year GH treatment in prepubertal iGHD children. Our results validate the published growth targets derived from the KIGS database.