Endocrine Abstracts

Introduction: Insulin-like growth factor 1 (IGF-1) is an established serum marker for both diagnosis of growth hormone (GH) deficiency and for monitoring treatment with Somatropin, whether it is recommended for the classic GH-insufficient short stature cases or for other GH-sufficient disorders.

Aim: To evaluate whether serum level of IGF-1 at diagnosis has a predictive value for the response to somatropin treatment during the 2 years of treatment in children with both GH-deficient and GH-sufficient short stature.

Materials and methods: We performed a retrospective study which included 192 children treated with somatropin for at least 2 years with variate causes of short stature (mean age 8.02±3.63, 71 boys, 121 girls). Patients were divided in GH-deficient and GH-sufficient based on peak GH value during stimulation tests with a cut off value of 7 ng/ml. Standard deviation score (SDS) was calculated for height and IGF-1 at diagnosis.

Results: SDS height gain at 2 years of treatment was positively correlated with SDS height gain at 6 months (r 0.549, P<0.0001) and 1 year (r 0.719, P<0.0001). SDS height gain at 2 years was negatively associated with male gender (beta −0.273, P 0.029) and baseline IGF-1 SDS (beta −0.249, P 0.001), after adjustment for age and diagnosis. When IGF-1 was introduced in the regression model as quartiles, the superior quartile was negatively associated with gain in height at 2 years (beta −0.361, P 0.043). SDS height gain at 6 months (beta 0.991, P<0.0001) and 1 year (beta 1.034, P<0.0001) of treatment were independently associated with SDS height gain at 2 years after adjustment for confounders.

Conclusion: Short children with highest IGF-1 SDS at diagnosis might have lower response to somatropin administration irrespective of GH reserve. However, the early response to somatropin administration independently predict the 2 year response to treatment, being a possible tool for guiding the therapeutic decision.