ABSTRACT
In healthy, young individuals blood sugar levels are maintained at approximately 5 mmol/l via a negative feedback loop. When blood sugar rises above 5 mmol/l insulin is released from the pancreas, which results in glucose being removed from circulation and immobilised as glycogen in the liver and muscles. When blood sugar levels drop below 5 mmol/l the pancreas releases glucagon that releases glycogen from the liver; the glycogen is broken down into glucose and released into the bloodstream, increasing blood sugar until insulin release is triggered. Insulin and glucagon are therefore mutually inhibiting. Deviations from the ‘set point’ for blood sugar, which tend to be due to the absorption of glucose from the gut, are rapidly regulated, whereas the mobilisation of glycogen means that blood sugar can be maintained even in early
starvation. Tight control of blood sugar is essential because the brain uses glucose as its ‘fuel but cannot store it-brain processes rely on a constant supply of glucose from the bloodstream.
