What is Diabetes Mellitus?

Diabetes mellitus is a group of metabolic diseases characterized by high blood sugar (glucose) levels, which result from defects in insulin secretion, or action, or both. Diabetes mellitus, commonly referred to as diabetes (as it will be in this article) was first identified as a disease associated with 搒weet urine," and excessive muscle loss in the ancient world. Elevated levels of blood glucose (hyperglycemia) lead to spillage of glucose into the urine, hence the term sweet urine. Normally, blood glucose levels are tightly controlled by insulin, a hormone produced by the pancreas. Insulin lowers the blood glucose level. When the blood glucose elevates (for example, after eating food), insulin is released from the pancreas to normalize the glucose level. In patients with diabetes, the absence or insufficient production of insulin causes hyperglycemia. Diabetes is a chronic medical condition, meaning that although it can be controlled, it lasts a lifetime.What is the impact of diabetes?Over time, diabetes can lead to blindness, kidney failure, and nerve damage. These types of damage are the result of damage to small vessels, referred to as microvascular disease. Diabetes is also an important factor in accelerating the hardening and narrowing of the arteriesatherosclerosis), leading to strokes, coronary heart disease, and other large blood vessel diseases. This is referred to as macrovascular disease. Diabetes affects approximately 17 million people (about 8% of the population) in the United States. In addition, an estimated additional 12 million people in the United States have diabetes and don't even know it. From an economic perspective, the total annual cost of diabetes in 1997 was estimated to be 98 billion dollars in the United States. The per capita cost resulting from diabetes in 1997 amounted to $10,071.00; while healthcare costs for people without diabetes incurred a per capita cost of $2,699.00. During this same year, 13.9 million days of hospital stay were attributed to diabetes, while 30.3 million physician office visits were diabetes related. Remember, these numbers reflect only the population in the United States. Globally, the statistics are staggering.Insufficient production of insulin (either absolutely or relative to the body's needs), production of defective insulin (which is uncommon), or the inability of cells to use insulin properly and efficiently leads to hyperglycemia and diabetes. This latter condition affects mostly the cells of muscle and fat tissues, and results in a condition known as "insulin resistance." This is the primary problem in type 2 diabetes. The absolute lack of insulin, usually secondary to a destructive process affecting the insulin producing beta cells in the pancreas, is the main disorder in type 1 diabetes. In type 2 diabetes, there also is a steady decline of beta cells that adds to the process of elevated blood sugars. For more, please read the Insulin Resistance article. Essentially, if someone is resistant to insulin, the body can, to some degree, increase production of insulin and overcome the level of resistance. After time, if production decreases and insulin cannot be released as vigorously, hyperglycemia develops.Glucose is a simple sugar found in food. Glucose is an essential nutrient that provides energy for the proper functioning of the body cells. Carbohydrates are broken down in the small intestine and the glucose in digested food is then absorbed by the intestinal cells into the bloodstream, and is carried by the bloodstream to all the cells in the body where it is utilized. However, glucose cannot enter the cells alone and needs insulin to aid in its transport into the cells. Without insulin, the cells become starved of glucose energy despite the presence of abundant glucose in the bloodstream. In certain types of diabetes, the cells' inability to utilize glucose gives rise to the ironic situation of "starvation in the midst of plenty". The abundant, unutilized glucose is wastefully excreted in the urine.Insulin is a hormone that is produced by specialized cells (beta cells) of the pancreas. (The pancreas is a deep-seated organ in the abdomen located behind the stomach.) In addition to helping glucose enter the cells, insulin is also important in tightly regulating the level of glucose in the blood. After a meal, the blood glucose level rises. In response to the increased glucose level, the pancreas normally releases more insulin into the bloodstream to help glucose enter the cells and lower blood glucose levels after a meal. When the blood glucose levels are lowered, the insulin release from the pancreas is turned down. It is important to note that even in the fasting state there is a low steady release of insulin than fluctuates a bit and helps to maintain a steady blood sugar level during fasting. In normal individuals, such a regulatory system helps to keep blood glucose levels in a tightly controlled range. As outlined above, in patients with diabetes, the insulin is either absent, relatively insufficient for the body's needs, or not used properly by the body. All of these factors cause elevated levels of blood glucose (hyperglycemia).Diabetes mellitus is a metabolic disorder characterized by a congenital (similar to juvenile-onset or Type I diabetes mellitus in people) or acquired (similar to adult-onset or Type II diabetes mellitus in people) inability to transport sugar from the bloodstream into cells. Once inside cells, sugar (glucose) is used to generate the energy that is essential for normal cellular function. Diabetes in animals is most commonly the acquired form and typically occurs in middle-aged to older pets. The disease results when glucose transport channels on cell membranes are insensitive to the effects of insulin (or when there are too few channels) or when the quantity of insulin produced by the pancreas is inadequate to activate the number of glucose channels needed to maintain normal cellular metabolism. In other words, insulin is the “key” that allows special “gates” for sugar transport across cell membranes to be opened. A diabetic, therefore, has too much glucose in the bloodstream where most of it cannot be utilized, and not enough glucose within the cells themselves, where it is most needed for energy. As a result, cells attempt to derive energy from alternate metabolic pathways, such as fat breakdown. Excessive use of these alternate energy pathways culminates in production of harmful by-products called ketones. The accumulation of ketones causes the body’s pH to become acidic (ketoacidosis) which makes the cellular environment inhospitable for normal metabolic functions. This condition can ultimately become life-threatening and requires aggressive medical therapy.Fortunately, most diabetics give some indication of their underlying condition, such as drinking and urinating excessively, before they develop ketoacidosis. Treating diabetics before they become ketotic is considerably more straightforward, safer, and of course less expensive than taking a "wait-and-see" approach to changes in drinking behavior. Equally important, diagnostic testing may reveal other serious conditions which can cause excessive urination and drinking, such as kidney or liver disease, adrenal hormone or electrolyte imbalances and uterus infections.