In the postabsorptive state, the glucose needs of the body are confined almost exclusively to those of the brain and erythron. These needs are met by hepatic release of glucose into the circulation, either by the breakdown of preformed glycogen (glycogenolysis) or by synthesis (gluconeogenesis) from glucose precursors. Gluconeogenesis occurs predominantly from lactate, pyruvate, alanine and glycerate, which are released into the circulation by somatic tissues, such as striatal muscle, during fasting.
