Insulin Growth Factor-Based Dosing of Growth Hormone Therapy in Children: A Randomized, Controlled Study

Abstract

Abstract Context: Weight-based dosing of GH is the standard of care for short children, although IGF-I is thought to be the main mediator of GH actions on growth. Objective: The objective of the study was to test whether IGF-I levels achieved during GH therapy are determinants of the growth responses to GH treatment. Design: This was a 2-yr, open-label, randomized, IGF-I concentration-controlled trial. Prepubertal short children [n = 172, mean age 7.53 yr, mean height sd score (HT-SDS) −2.64] with low IGF-I levels (mean IGF-I SDS −3.56) were randomized to receive one of two GH dose-titration arms in which GH dosage was titrated to achieve an IGF-I SDS at the mean [IGF(low) group, n = 70] or the upper limit of the normal range [+2 SDS, IGF(high) group, n = 68] or to a comparison group of conventional GH dose of 40 μg/kg/d (n = 34). Setting: The study was conducted in a multicenter, outpatient setting. Primary Outcome Measure: Change in HT-SDS over 2 yr was measured. Results: One hundred forty-seven patients completed the trial. Target IGF-I levels were achieved in the dose-titration arms within 6–9 months. The changes in HT-SDS were +1.0, +1.1, and +1.6 for conventional, IGF(low), and IGF(high), respectively, with IGF(high) showing significantly greater linear growth response (P < 0.001, compared with the other two groups). The IGF(high) arm required higher doses (>2.5 times) than the IGF(low) arm, and these GH doses were highly variable (20–346 μg/kg/d). Multivariate analyses suggested that the rise in the IGF-I SDS significantly impacted height outcome along with the GH dose and the pretreatment peak-stimulated GH level. Conclusion: IGF-I-based GH dosing is clinically feasible and allows maintaining serum IGF-I concentrations within the desired target range. Titrating the GH dose to achieve higher IGF-I targets results in improved growth responses, although at higher average GH doses.