Abstract
Growth hormone (GH) is a major regulator of postnatal growth and metabolism. There are extensive clinical applications for GH or its antagonists, including treatments for dwarfism, cancer and metabolic wasting. Owing to this, there is considerable interest in the mechanisms of GH receptor (GHR) activation. It is conventionally thought that GH induces dimerization of two GHR monomers, which initiates intracellular signaling cascades. However, recent studies have provided evidence for a ligand-induced conformational change within constitutively dimerized GHRs being responsible for activating signaling pathways. This review will relate the new model of GHR activation to the activation of related cytokine receptors and discuss the implication of this new model for the design of small GH mimetics and antagonists for therapeutic use.