Insulin molecule. Computer artwork of a molecule of insulin showing its primary (rods) and secondary (helices) structures. Insulin is a hormone produced by the pancreas. It consists of two peptide chains, A and B, which are linked by disulphide bridges. This is the hexamer form of the hormone, containing three of each subunit. Insulin is released from the pancreas when blood sugar levels are high, for example after a meal. It instructs liver, muscle and fat cells to absorb the glucose and store it as glycogen (liver and muscle) or fat. Insufficient production of insulin leads to an accumulation of glucose in the blood causing diabetes.