Is a Two-Year Growth Response to Growth Hormone Treatment a Better Predictor of Poor Adult Height Outcome Than a First-Year Growth Response in Prepubertal Children With Growth Hormone Deficiency?

Objective: The first year response to growth hormone (GH) treatment is related to the total height gain in GH treated children, but an individual poor first year response is a weak predictor of a poor total GH effect in GH deficient (GHD) children. We investigated whether an underwhelming growth response after 2 years might be a better predictor of poor adult height (AH) outcome after GH treatment in GHD children. Design and methods: Height data of GHD children treated with GH for at least 4 consecutive years of which at least two prepubertal and who attained (near) (n)AH were retrieved from the Belgian Register for GH treated children (n = 110, 63% boys). In ROC analyses, the change in height (ΔHt) SDS after the first and second GH treatment years were tested as predictors of poor AH outcome defined as: (1) nAH SDS <-2.0, or (2) nAH SDS minus mid-parental height SDS <-1.3, or (3) total ΔHt SDS <1.0. The cut-offs for ΔHt SDS and its sensitivity at a 95% specificity level to detect poor AH outcome were determined. Results: Eleven percent of the cohort had a total ΔHt SDS <1.0. ROC curve testing of first and second years ΔHt SDS as a predictor for total ΔHt SDS <1.0 had an AUC >70%. First-year ΔHt SDS <0.41 correctly identified 42% of the patients with poor AH outcome at a 95% specificity level, resulting in respectively 5/12 (4.6%) correctly identified poor final responders and 5/98 (4.5%) misclassified good final responders (ratio 1.0). ΔHt SDS after 2 prepubertal years had a cut-off level of 0.65 and a sensitivity of 50% at a 95% specificity level, resulting in respectively 6/12 (5.5%) correctly identified poor final responders and 5/98 (4.5%) misclassified good final responders (ratio 1.2). Conclusion: In GHD children the growth response after 2 prepubertal years of GH treatment did not meaningfully improve the prediction of poor AH outcome after GH treatment compared to first-year growth response parameters. Therefore, the decision to re-evaluate the diagnosis or adapt the GH dose in case of poor response after 1 year should not be postponed for another year.