The use of exogenous GH to increase its circulating concentration, may benefit critically ill patients by increasing their nitrogen retention and promoting the wound healing process. GH also changes protein production in wounds, causes higher levels of insulin and changes substrate utilization. Its effects are anabolic, diabetogenic and lipolytic, acting through both direct and indirect mechanisms. The effects on carbohydrate and fat metabolism are directly mediated through specific GH receptors, while its effect on protein is mediated through IGF-I. Its effects on IGF-I production and the induction of IGF binding proteins are currently being studied in an effort to better understand the mechanism of GH actions during stress.