Significant increase of IGF-I concentration and of IGF-I/IGFBP-3 molar ratio in generation test predicts the good response to growth hormone (GH) therapy in children with short stature and normal results of GH stimulating tests.
ABSTRACT BACKGROUND: Insulin-like growth factor-I (IGF-I) generation test has been introduced for the assessment of growth hormone (GH) sensitivity, however, its significance in predicting growth response to GH therapy has also been brought up. The molar ratio of IGF-I to its binding protein-3 (IGFBP-3) determines IGF-I bioavailability. Aims: Evaluation of usefulness of IGF-I and IGFBP-3 generation test in predicting the effectiveness of rhGH therapy in children with short stature. PATIENTS AND METHODS: The analysis comprised 60 children with short stature, normal results of GH stimulating tests but decreased IGF-I secretion. In all the patients, GH insensitivity was excluded on the basis of IGF-I and IGFBP-3 generation test. Next, GH therapy was administered and height velocity (HV), together with IGF-I and IGFBP-3 secretion, was assessed every year, during 3 years. The comparative group consisted of 30 children with partial GH deficiency (pGHD). RESULTS: Both IGF-I secretion and IGF-I/IGFBP-3 molar ratio increased significantly during generation test (p<0.05) and - further - during GH therapy (however insignificantly), together with at least doubling of pretreatment HV. There was no significant difference between the studied group of patients and children with pGHD. CONCLUSIONS: Significant increase of IGF-I in generation test speaks for GH therapy effectiveness in short children, despite normal results of GH stimulating tests.