We developed a Cre-LoxP model for tissue specific deletion of the Growth Hormone Receptor(GHR).We now have established cell lines of liver specific, muscle specific and fat specific GHR deletion to study phenotypic impact at the whole animal and tissue level in terms of signal transduction and glucose or fat metabolism.These models provide a unique opportunity to examine the distinct contribution of GH versus IGF-I in body, organ and tissue growth as well as to define the cellular/molecular mechanisms by which GH induces insulin resistance and contributes to diabetes mellitus and aging.