Chapter 7 - Pancreatic Hormones: Insulin and Glucagon

Abstract

This chapter discusses pancreatic hormones such as insulin and glucagon. A feature essential for life of higher vertebrates is their ability to maintain a relatively constant blood glucose concentration. In the higher animals, glucose is essential as an energy source for all cells. Although some cells can utilize alternate fuel metabolites such as amino acids or fatty acids, the brain and its neurons are dependent upon a continuous supply of blood-delivered glucose. Superimposed on the requirement for the maintenance of a constant blood glucose level are the perturbations in blood glucose that may naturally occur as a consequence of ongoing physiological and metabolic events. Insulin is a potent hormone in that it has a wide sphere of influence; directly or indirectly it affects virtually every organ and tissue in the body. The main functions of insulin are to stimulate anabolic reactions for carbohydrates, proteins, and fats; all of which will have the metabolic consequences of producing a lowered blood glucose level. Glucagon can be thought of as an indirect antagonist of insulin. Glucagon stimulates catabolic reactions that lead ultimately to an elevation of blood glucose levels. Pancreas is continuously adjusting the relative amounts of glucagon and insulin secreted in response to the continuous perturbations of blood glucose and other fuel metabolites occurring as a consequence of changes in anabolism and catabolism in the various tissues.