Insulin is the key hormone of carbohydrate metabolism, it also influences the metabolism of fat and proteins. It lowers blood glucose by increasing glucose transport in muscle and adipose tissue and stimulates the synthesis of glycogen, fat, and protein. The anabolic action of insulin is antagonized by the catabolic action of glucagon. This hormone stimulates glycogenolysis and gluconeogenesis. The molar insulin: glucagon ratio is a parameter for an anabolic or a catabolic situation. Epinephrine also antagonizes insulin action. Like glucagon it stimulates glycogenolysis. In addition it reduces the insulin sensitivity of peripheral tissues and inhibits the release of insulin. Growth hormone decreases glucose uptake in muscle and adipose tissue gluconeogenesis in liver. In the presence of insulin, growth hormone stimulates protein synthesis. The net metabolic effects of a single hormone are directly related to the activity of other synergistic or antagonistic hormones.