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.