ESPE Abstracts

Background: After 50 years of hGH use for GH deficient (GHD) children the definition of the adequate hGH substitution dose and response remain uncertain.

Objective and hypotheses: We hypothesized that subjects with GHD caused by congenital pituitary defects constitute an ideal model for defining substitution dose of hGH. Consequently, an appropriate study group was formed and pertinent long-term data were retrospectively analyzed.

Method: A total of 18 patients (12 boys and six girls) were included in the study: 12 with pituitary stalk interruption syndrome (PSIS), five with Prop1 and one with SHH gene mutations.

Results: In boys, age at GHRx initiation was 5.3±1.9 years, first year growth velocity (GV) 11.6±2.2 cm, final height (FH) 175.3±3.6 cm with a target height (TH) 169.9±4.2 cm. In girls, age at GHRx initiation was 9.8±2.6 years, first year GV 9.4±2.2 cm, FH 160±4.2 cm with a TH 160.4±4.1. First year GV in all patients fell within limits suggested as adequate first year response (Bakker et al., 2008). The mean GH dose throughout the treatment period was 0.140 mg/kg per week.

Conclusion: A GHRx dose of 0.140 mg/kg per week appears to be an adequate substitution therapy in GHD children offering a good first year GV and a FH well within or above the TH range. The better outcome in boys must be attributed to earlier therapy initiation rather than gender difference in responsiveness. It seems that currently recommended GHRx doses are supra-substituting doses apparently needed to overcome obstacles such as deficient hGH responsiveness and growth failure from other factors. In such cases, a search for other causes of deficient response or the use of prediction models may offer an improved outcome.