Insulin is a peptide hormone produced by the pancreas, an organ of the digestive tract. Insulin is synthesized in the beta cells of the organ. It is a fundamental hormone used in the utilization of glucose in the body. In healthy individuals, secretion of insulin follows either ingestion of a meal or presence of sugar in the blood. Principal action of insulin is to transport sugar from the blood into individual cells so as to ensure normal cellular function. It achieves this by forming channels on cell membranes that allow glucose into the cells. In the liver, insulin promotes formation of glycogen and decreases synthesis of glucose. In the fat tissue, it promotes the uptake of glucose and formation of fat and prevents breakdown of fat as a source of energy. Insulin has a body building effect. This occurs in the skeletal muscle where it promotes protein synthesis resulting in an increase in the bulk of muscle.