Effect of Insulin Sensitization on Insulin Like Growth Factor-1 Responses to Growth Hormone Treatment in Children Born Small for Gestational Age

Growth hormone treatment (GH) is recommended in children born small for gestational age (SGA) who fail to catch-up. SGA is a heterogeneous condition as reflected in the varied response to GH treatment. Variable generation and resistance to Insulin-like growth factor-1 (IGF-1), the most important circulating mediator of GH action may underpin this heterogeneity. An association between the variants in the genes related to lower insulin sensitivity and reduced IGF-1 and growth response to GH therapy in SGA children have been reported recently. The hypothesis of this study is that insulin sensitivity may be causally linked to the response to GH therapy, and adjuvant therapy with an insulin sensitizer may improve IGF-1 generation, decrease IGF-I resistance and optimise growth response.

To explore this hypothesis, this study aims to determine the effects of insulin sensitization using Metformin as an adjuvant to a fixed dose GH therapy for 6 months in short SGA children. The patients will be short SGA children between age 4 -10 years and identified from three paediatric endocrine units in Denmark, Ireland and the United Kingdom. In this mechanistic study 24 subjects starting GH treatment will be randomised in a 1:1 ratio to adjunctive Metformin or placebo for 6 months and followed-up for another 6months. The participants will receive GH treatment for the entire duration of the study (12 months) and will undergo an oral glucose tolerance test and dual-energy x-ray absorptiometry scan to determine glucose metabolism and body fat mass respectively at baseline and 6 months, and will have 3 monthly measurements of height, weight and skinfold thickness. The primary outcome will be the area under the curve of IGF-1 levels measured at 0, 1, 3 and 6 months. Secondary outcomes will include changes in insulin sensitivity, height, body fat mass and safety measures at 6 and 12 months.