Prediction of height velocity of prepubertal children with growth hormone deficiency in the first year of treatment with recombinant human growth hormone

The association between growth response to growth hormone and baseline body composition of children with growth hormone deficiency

OBJECTIVE

We wanted to examine the relationship between initial growth response to recombinant human Growth Hormone (rhGH) treatment and body composition in children with growth hormone deficiency (GHD).

DESIGN AND METHODS

Forty-two patients (21 boys and 21 girls) aged between 5.7-15.5 years (mean age: 10.8 ± 2.6 years) with isolated GHD. The auxological and laboratory data (GH and IGF-I levels) and results of bioelectrical impedance analyses were evaluated. Children with GHD were followed up for 12 months and categorized according to growth response to rhGH into good and poor responders (change in height of > 0.7 SDS or < 0.7 SDS over one year respectively). Mean doses of rhGH per kg of fat free mass (FFM) were calculated.

RESULTS

Forty-eight percent of patients showed a good growth response to rhGH therapy. At study entry, mean age, height SDS, weight SDS, serum IGF-1 SDS, IGFBP-3 SDS, growth velocity prior to rhGH therapy, GH after clonidine and l-dopa were similar in the two groups. At baseline, BMI SDS and waist-hip ratio were significantly higher in good responders (p = 0.02 and p = 0.006, respectively). Good responders had lower percentages of FFM (73.4 ± 8.9 vs. 83.1 ± 5.9) and total body water (TBW) (56.5 ± 5.3 vs. 63.1 ± 4.4), compared to poor responders (p < 0.05). There were significant correlations between changes in height SDS over one year and baseline body composition in children with GHD on rhGH treatment (r = -0.617 for percentage of FFM, r = -0.629 for percentage of TBW, p < 0.001). A correlation between BMI SDS, waist-hip ratio, mean rhGH dose per FFM and growth response was observed only in prepubertal subjects.

CONCLUSION

Baseline body composition data in children with GHD can be used to predict the growth response to rhGH treatment. A management strategy that involves titrating rhGH dose according to FFM as a means of optimizing the growth response to intervention requires further study.

Predicting the growth response of children with idiopathic growth hormone deficiency to one year of recombinant growth hormone treatment: derivation and validation of a useful method

Patients with idiopathic growth hormone (GH) deficiency (iGHD) show a wide interindividual variability in their response to recombinant GH (rGH) therapy. Accurate growth prediction would provide clinicians a helpful tool for planning and optimizing growth promoting therapy. We develop and validate a model to predict the growth response, using accessible parameters and simple calculations. Data of 132 prepubertal patients with iGHD, receiving rGH treatment for at least one year, were collected. The sample was split into two statistically similar groups: a derivation set (100 children) and a validation set (32 children). Linear multiple regression, stepwise analysis, was used to derive the model. Validation was performed by calculating the difference in predictive power when applying it to the validation group ('shrinkage'), and analyzing the differences between the predicted and observed responses ('studentized residual'). The obtained prediction model predicts 97.8% of the variability of height achieved after one year of therapy (error SD = 1.767 cm). All data integrated in our model are accessible to the clinician when evaluating the patient and the calculations are fast and simple. It is an accurate method that fulfills all the requirements for becoming a useful tool to predict growth response in prepubertal children with iGHD and should be helpful optimizing rGH therapy.