Life for a person with diabetes mellitus means constant awareness of the illness--one or two insulin shots a day, frequent finger punctures to monitor blood glucose level, a restrictive diet, and concern over complications, which include loss of vision, leg ulcers, and kidney damage. The many symptoms of diabetes reflect disturbances in carbohydrate, protein, and fat metabolism.
Diabetes in Latin means increased urine output, and mellitus means honey, referring to urine's sugar content. Lack of insulin decreases movement of glucose into skeletal muscle and adipose cells, inhibiting glycogen formation. As a result, blood sugar concentration rises (hyperglycemia). When blood sugar reaches a certain level, the kidneys begin to excrete the excess, and glucose appears in the urine (glycosuria). The osmotic pressure of water follows the glucose by osmosis, causing excess urinary water loss. As a result, the person becomes dehydrated and very thirsty.
Diabetes mellitus decreased protein synthesis, causing tissues to waste away as glucose-starved cells use protein as an energy source. Weight falls and wounds cannot heal. Fatty acids accumulate in the blood as a result of decreased fat synthesis and storage. Ketone bodies, a by-product of fat metabolism, also increase in the blood. They are excreted in the urine as sodium salts, and large quantities of water follow by osmosis, intensifying dehydration and lowering sodium concentration in the blood. Accumulation of ketones and loss of sodium ions lead to metablic acidosis, a condition that lowers the pH of body fluids. Acidosis and dehydration adversely affect brain neurons. Without treatment (insulin replacement), the person becomes disoriented and may enter a diabetic coma and die.
There are two common forms of diabetes mellitus. Insulin-dependent diabetes mellitus (IDDM, also called type 1, or juvenile onset diabetes) usually appears before age 20. About 15% of the 11 million Americans with diabetes mellitus have this form. It is an autoimmune disorder attacking pancreatic beta cells, ultimately destroying them so that insulin secretion halts. Treatment is administering enough insulin to control carbohydrate metabolism. Insulin cannot be taken in oral form because it is a peptide and digestive enzymes break it down.
The milder, other common form of diabetes, non-insulin-dependent diabetes mellitus (NIDDM), begins gradually, in people over 40. Usually in NIDDM cells lose insulin receptors, and therefore cannot respond to insulin, even if it is abundant. Heredity and a lifestyle of overeating and underexercising are risk factors for developing NIDDM. People who develop it are often overweight. Treatment for NIDDM includes careful control of diet to avoid foods that stimulate insulin production, exercising, and maintaining desirable body weight.
The glucose-tolerance test is used to diagnose diabetes mellitus. The patient ingests a known amount of glucose, and blood glucose concentration is measured at intervals to determine glucose utilization. If the person has diabetes, blood glucose concentration rises excessively and remains elevated for several hours. In a healthy person, glucose rise is less dramatic and the level returns to normal in about one and half hours.