• Height velocity during the first year [ Time Frame: One year ] [ Designated as safety issue: No ]
• Change in height standard deviation (SD) score [ Time Frame: One year ] [ Designated as safety issue: No ]

• Change in height velocity from the pretreatment height velocity over 1 year
• Change in height standard deviation (SD) score over 1 year

• Changes in serum concentrations of IGF-1, IGF-2, insulin-like growth factor binding protein-2 (IGFBP-2) and insulin-like growth factor binding protein-3 (IGFBP-3) during the course of the study [ Time Frame: One year ] [ Designated as safety issue: No ]
• Changes in bone age over one year [ Time Frame: One year ] [ Designated as safety issue: No ]
• IGF generation test: serum IGF-1 and IGFBP-3 changes after 7 days exposure to recombinant human growth hormone (rhGH) [ Time Frame: Seven days ] [ Designated as safety issue: No ]

• Changes in serum concentrations of IGF-1, IGF-2, insulin-like growth factor binding protein-2 (IGFBP-2) and insulin-like growth factor binding protein-3 (IGFBP-3) during the course of the study
• Changes in bone age over one year
• IGF generation test: serum IGF-1 and IGFBP-3 changes after 7 days exposure to recombinant human growth hormone (rhGH)

This study is intended to determine whether dosing with recombinant human insulin-like growth factor (rhIGF-1) will safely and effectively increase the growth of prepubertal children with low IGF-1 levels but who produce sufficient growth hormone (GH). Subjects will be randomized to either an observation arm or to active treatment.

Prepubertal growth failure associated with primary IGF-1 deficiency (IGFD). Primary IGFD is a term that has been used to describe patients with intrinsic cellular defects in GH action. In this protocol, primary IGFD is defined as short stature (<-2 standard deviations [SDs] below the mean for age and gender), abnormal serum IGF-1 (<-2 SDS below the mean for age and gender), and levels of growth hormone (GH) that are normal (≥7ng/mL) after a GH stimulation test. Primary IGFD is believed to result from a lower than normal ability to produce IGF-1 when exposed to normal levels of GH, i.e., a type of GH insensitivity of GH resistance.

This trial is a randomized, open label, observation-controlled, parallel-dose comparison efficacy and safety study conducted in approximately 40 centers across the United States.

• Growth Disorders
• Insulin-Like Growth Factor-1 Deficiency

Inclusion Criteria:

• Ages 3-10 years inclusive for girls; ages 3-11 years inclusive for boys
• Prepubertal
• Height SD score of < -2
• IGF-1 SD score of < -2

Exclusion Criteria:

• Prior treatment with GH, IGF-1, or other growth-influencing medications
• Growth failure associated with other identifiable causes (e.g., syndromes, chromosomal abnormality)
• Chronic illness such as diabetes, cystic fibrosis, etc.