Читать книгу Transitions in Care - Howard A. Wolpert - Страница 16

Before we get to the principles about how to achieve good blood glucose control, we’re going to present a brief review of how insulin regulates glucose metabolism in the body. As you probably know, insulin is a hormone produced by the beta-cells in the pancreas. There are two different components to the insulin in circulation (see Figure 1):

Background insulin (also commonly referred to as basal insulin) controls the blood glucose levels in between meals and overnight. During these periods, the liver (which acts like the body’s glucose reservoir) is continuously releasing glucose into the bloodstream to provide energy for basic functions in the body. Insulin helps control this process. Without basal insulin, there would be an excessive release of glucose by the liver, and glucose levels in the blood would rise. In addition, in the absence of basal insulin, the liver starts producing ketone bodies, and these can accumulate in the blood, leading to a dangerous condition known as diabetic ketoacidosis.

Insulin surges at mealtimes (also commonly referred to as insulin boluses) cause the tissues of the body to take up glucose from the bloodstream. The amount of insulin produced in these mealtime surges is precisely controlled to ensure that there is just enough to take care of the carbohydrates being eaten. Eat a bit more, and more insulin is produced; eat a bit less, and less insulin is produced.

FIGURE 1 A 24-hour insulin and glucose profile in a person without diabetes.

In type 1 diabetes, the immune system (which is normally involved in combating infections) misguidedly attacks and destroys the beta-cells in the pancreas. The end result is that the body can no longer produce insulin. The fundamental challenge in treating type 1 diabetes is in replacing the insulin your body is no longer making and taking just enough insulin to match your body’s needs. Too much insulin leads to low blood glucose levels and too little leads to high blood glucose. Trying to avoid large ups and downs in your glucose numbers is another challenge in treating type 1 diabetes; dramatic variations in your numbers can be particularly unpleasant.