• Change in height SDS [ Time Frame: during the first year of treatment ] [ Designated as safety issue: No ]
• Safety assessments including: physical exam, funduscopic exams, adverse events, safety and metabolic labs and anti-GH and anti-IGF-1 antibodies [ Time Frame: during treatment ] [ Designated as safety issue: Yes ]
• Changes in serum concentrations of GH, IGF-1, IGFBP-1, IGFPB-3, ALS and GHBP [ Time Frame: during treatment ] [ Designated as safety issue: No ]
• Change in bone age [ Time Frame: during treatment ] [ Designated as safety issue: No ]
• Changes in adipokines [ Time Frame: during treatment ] [ Designated as safety issue: No ]

IGF-1 (insulin-like growth factor-1) is a hormone that is normally produced in the body in response to another hormone called growth hormone. Growth Hormone is produced by a small gland at the base of the brain (the pituitary). Together IGF-1 and GH are large contributors to growth during infancy, childhood, and adolescence.

Children with IGF Deficiency are short and have an imbalance in the levels of growth hormone and IGF-1 that their body produces. Their growth hormone levels are normal or even high, but IGF-1 levels do not increase normally in response to growth hormone. As a result, they have a type of growth hormone insensitivity and an inability to grow normally.

This study is a test to see whether daily dosing with a combination of rhIGF-1 and rhGH will help children with IGFD grow taller more quickly than children treated with rhGH alone. The study medications, rhIGF-1 and rhGH, are approved by the US Food and Drug Administration (FDA) for use in some growth disorders in children, but the combination of rhIGF-1 and rhGH in children with IGF-1 deficiency (IGFD) is investigational.

• Drug: somatropin
• Drug: mecasermin and somatropin

• Active Comparator: rhGH 45µg/kg once daily injection
• Experimental: rhGH 45µg/kg and rhIGH-1 50µg/kg once daily injection
• Experimental: rhGH 45µg/kg and rhIGH-1 100µg/kg once daily injection
• Experimental: rhGH 45µg/kg and rhIGH-1 150µg/kg once daily injection

Inclusion Criteria:

• Parents or legally authorized representatives must give signed informed consent before any trial-related activities
• IGF-1 SDS of ≤ -1 for age and gender
• Short stature, as defined by a height SDS of ≤ -2 for age and gender
• Chronological age ≥ 5 years
• Bone age ≤ 11 years in boys and ≤ 9 years in girls
• GH sufficiency, defined as a maximal stimulated GH response of greater than or equal to 10 ng/mL at Visit 2 (note: upon approval of the Medical Monitor, the result of a prior GH stimulation test may satisfy this requirement).
• Prepubertal status
• Adequate nutrition as evidenced by a body mass index (BMI) greater than or equal to the 5th percentile for age and gender

Exclusion Criteria:

• Severe Primary IGFD (defined as height and IGF-1 SDS ≤ 3, and stimulated GH response greater than or equal to 10 ng/mL)
• Prior or current use of medications with the potential to alter growth patterns including GH, IGF-1, IGFBP-3, gonadotrophin agonists (e.g., Lupron), aromatase inhibitors, androgens and estrogens
• Known or suspected allergy to rhGH, rhIGF-1 or a constituent of their formulations
• Current use of medications for attention deficit disorder
• A chronic health condition that requires anti-inflammatory steroids or daily medication unless approved by the Medical Monitor