For the long-term treatment of growth failure in children and adolescents from 2 to 18 years with confirmed severe primary insulin-like growth factor-1 deficiency (Primary IGFD).Severe Primary IGFD is defined by:* height standard deviation score ≤–3.0and* basal IGF-1 levels below the 2.5th percentile for age and genderand* GH sufficiency.* Exclusion of secondary forms of IGF-1 deficiency, such as malnutrition, hypothyroidism, or chronic treatment with pharmacologic doses of anti-inflammatory steroids.Severe Primary IGFD includes patients with mutations in the GH receptor (GHR), post-GHR signaling pathway, and IGF-1 gene defects; they are not GH deficient, and therefore, they cannot be expected to respond adequately to exogenous GH treatment.In some cases, when deemed necessary, the physician may decide to assist in the diagnosis by performing an IGF-I generation test.