Introduction: Rosenfeld, R.G.; Overview of the IGF-I System: Cohen, P.; Defining Insulin-Like Growth Factor-I Deficiency: Ranke, M.B.; Molecular Mechanisms of IGF-I Deficiency: Rosenfeld, R.G.; Treatment of Insulin-Like Growth Factor Deficiency with IGF-I: Studies in Humans: Backeljauw, P.F.; Chernausek, S.D.; Patient Selection for IGF-I Therapy: Clayton, P.E.; Ayoola, O.; Whatmore, A.J..