This book addresses a wide range of basic and clinical issues in the physiology and pharmacology of growth hormone. The volume is organized like a textbook. It begins with factors contributing to GH gene expression, the functional relationships of the GH receptor, molecular biological analysis of the GH-GH receptor complex and proceeds to describe the insulin-like growth factor axis. Transgenic models are discussed for analysis of discrete effects. These discussions provide a bridge to clinically oriented discussions of growth abnormalities in GH deficient children, GH insensitivity due to deficiency of the GH receptor, and the concept of aging as a GH/IGF-I deficiency state. Discussions also include the immune system as a source and a responder to GH, GHRH, IGF-I and the effects of GH excess.