Recombinant human insulin-like growth factor-I therapy for children with growth disorders

Until recently, the only possible therapy available for treatment of children with significant short stature was recombinant human growth hormone (rhGH). However, recombinant human insulin-like growth factor-I (rhIGF-I) has now become commercially available as a therapeutic option to treat children of short stature caused by severe primary IGF-I deficiency, defined as: height standard deviation score (SDS) less than or equal to -3.0, basal IGF-I SDS less than or equal to -3.0, and normal or elevated levels of GH. Published data demonstrate that rhIGF-I therapy in patients with primary IGF-I deficiency accelerates growth significantly during the first year of treatment, but progressive attenuation is likely in subsequent years. The growth response to rhIGF-I is neither as intense nor as well sustained as the growth response to rhGH among children with GH deficiency. Despite increasing interest in the possibility for broader use of rhIGF-I for growth promotion, especially in children with idiopathic short stature (ISS), it is necessary to wait for studies assessing the efficacy and safety of rhIGF-I therapy in this condition. In this particular population (ISS patients), the combination of rhIGF-I and rhGH, compared with either hormone used alone, may have theoretical advantages. Hypoglycemia has been the most common side effect reported with use of rhIGF-I and is reasonably controlled with adequate food intake. Most of the other (long-term) adverse effects appear to be related to hyperstimulation of lymphoid tissue growth. Little is known about the long-term effects of IGF-I therapy in growing children, but caution and long-term, controlled, prospective trials of rhIGF-I-treated children and adolescents are needed.