One of the most frustrating things that diabetics deal with is an unexpected rise in blood glucose overnight. You go to bed with a BG of 100 mg/dL (5.6 mmol/L), and wake up with a BG of 130 (7.2)! You didn't eat, so what happened?
This results from two distinctly different processes: Dawn Phenomenon and Somogyi Effect. Here are some basics.
Everyone, diabetic or not, exhibits some Dawn Phenomenon. It is a natural part of our bodies' circadian rhythms. Some have said it is the way our ancestors had the strength to rise and slay a wooly behemoth for breakfast.
Since most of us fast while sleeping, with teenagers a possible exception, our bodies use stored energy during sleep. If you have read our Nutrition Section, you know that the body uses all three macro-nutrients (carbohydrates, proteins, and fats) to store energy.
The most easily used is the storage medium of carbohydrates, called glycogen. Glycogen is made from glucose, and is stored in the liver and muscles. Since it is basically nothing more than a complex matrix of glucose, it is easy for the body to store and use, something the body does all day long. The technical term for the act of creating and storing glycogen is glycogenesis. When the body calls for the conversion of glycogen back to glucose it is called glycogenolysis.
Another macro-nutrient that is available to be converted to glucose is protein. Most of us think of our protein as being stored in muscle, but the body has protective mechanisms to make muscle wasting its last choice. One of the most useful and readily available sources of protein storage is in blood components, i.e., albumin (plasma). The body uses a process performed in the liver to convert amino acids, the building blocks of proteins, into glucose. The name for this process is gluconeogenesis, literally "the creation of new glucose".
So, what does all this have to do with a high fasting BG? Overnight, usually between 4am and 11am, your body releases some hormones. These are Growth Hormone (GH) from the anterior pituitary gland, cortisol from the adrenal cortex, glucagon from your pancreatic alpha-cells, and epinephrine (adrenalin). These hormones cause an increase in insulin resistance, raising your BG. In addition, these hormones trigger glycogenolysis and gluconeogenesis, adding stored or new glucose to your bloodstream
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