Insulin is secreted when blood glucose levels rise above normal values. One of the most important effects of insulin is to facilitate the transport of glucose across plasma membranes, allowing the diffusion of glucose from blood into most body cells. It also stimulates the production of glycogen from glucose. The glucose is then stored in the liver to be released when blood glucose levels drop.
The availability of synthesized insulin has allowed a vastly improved quality of life for diabetics. © iStockphoto.com/Dave Parker.