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 (height standard deviation score[SDS]<-2 below the mean for age and gender), low serum IGF-1 (IGF-1 SDS <-2 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 or GH resistance.