Porth's Essentials of Pathophysiology, 4e

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Diabetes Mellitus and the Metabolic Syndrome

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result in normoglycemia and proper weight gain, and prevent ketosis. 3 If dietary management alone does not achieve a capillary blood glucose of 90 to 99 mg/dL or a 2-hour postprandial blood glucose less than 120 mg/dL, the Fifth International Workshop on GDM recommends therapy with insulin. 28 More recently, several oral agents have also been used for the treatment of GDM, includ- ing glyburide and metformin. Self-monitoring of blood glucose levels is essential. Approximately 50% of women with GDM will develop type 2 diabetes within 5 to 10 years. 26 Women in whom GDM is diagnosed should be followed after delivery to detect diabetes early in its course. These women should be evaluated during their first postpar- tum visit with a 2-hour OGTT with a 75-g glucose load. Clinical Manifestations of Diabetes Diabetes mellitus may have a rapid or an insidious onset. In type 1 diabetes, signs and symptoms often arise suddenly. Type 2 diabetes usually develops more insidi- ously; its presence may be detected during a routine medical examination or when a patient seeks medical care for other reasons. The most commonly identified signs and symptoms of diabetes are often referred to as the three polys: (1) polyuria (i.e., excessive urination), (2) polydipsia (i.e., excessive thirst), and (3) polyphagia (i.e., excessive hunger). These three symptoms are closely related to the hyperglycemia and glycosuria of diabetes. Glucose is a small, osmotically active molecule. When blood glucose levels are sufficiently elevated, the amount of glucose filtered by the glomeruli of the kidney exceeds the amount that can be reabsorbed by the renal tubules; this results in glycosuria accompanied by large losses of water in the urine. Thirst results from the intracellu- lar dehydration that occurs as blood glucose levels rise and water is pulled out of body cells, including those in the hypothalamic thirst center. This early symptom may be easily overlooked in people with type 2 dia- betes, particularly in those who have had a gradual increase in blood glucose levels. Polyphagia usually is not present in people with type 2 diabetes. In type 1 diabetes, it probably results from cellular starvation and the depletion of cellular stores of carbohydrates, fats, and proteins. Weight loss despite normal or increased appetite is a common occurrence in people with uncontrolled type 1 diabetes. The cause of weight loss is twofold. First, loss of body fluids results from osmotic diuresis. Vomiting may exaggerate the fluid loss in ketoacidosis. Second, body tissue is lost because the lack of insulin forces the body to use its fat stores and cellular proteins as sources of energy. In terms of weight loss, there often is a marked difference between type 2 diabetes and type 1 diabetes. Many people with uncomplicated type 2 diabetes often have problems with obesity. Other signs and symptoms of hyperglycemia include recurrent blurred vision, fatigue, paresthesias, and skin infections. In type 2 diabetes, these often are the

symptoms that prompt a person to seek medical treat- ment. Blurred vision develops as the lens and retina are exposed to hyperosmolar fluids. Lowered plasma volume produces weakness and fatigue. Paresthesias reflect a temporary dysfunction of the peripheral sensory nerves. Chronic skin infections can occur and are more com- mon in people with type 2 diabetes. Hyperglycemia and glycosuria favor the growth of yeast organisms. Pruritus and vulvovaginitis due to Candida infections are com- mon initial complaints in women with diabetes. Balanitis secondary to Candida infections can occur in men. DiagnosticTests The diagnosis of diabetes mellitus is confirmed through the use of laboratory tests that measure blood glucose levels. Testing for diabetes should be considered in all individuals 45 years of age and older. Diabetes screen- ing should be considered at a younger age in people who are obese, have a first-degree relative with diabetes, are members of a high-risk group, have delivered an infant weighing more than 9 pounds or been diagnosed with GDM, have hypertension or hyperlipidemia, or have met the criteria (IFG, IGT, elevated A1C) for increased risk of diabetes on previous testing. 28 BloodTests Blood glucose measurements are used in both the diagnosis and management of diabetes. Diagnostic tests include the FPG, casual plasma glucose, the glu- cose tolerance test, and glycosylated hemoglobin (i.e., A1C). 10,11,28 Laboratory and capillary or finger-stick glu- cose tests are used for glucose management in people with diagnosed diabetes. Fasting Plasma Glucose. The FPG represents plasma glucose levels after food has been withheld for at least 8 hours. Advantages of the FPG are convenience, patient acceptability, and cost. An FPG level below 100 mg/dL (5.6 mmol/L) is considered normal (see Table 33-3). Casual Blood Glucose Test. A casual (or random) plasma glucose is one that is done without regard to the time of the last meal. A casual plasma glucose con- centration that is unequivocally elevated ( ≥ 200 mg/dL [11.1 mmol/L]) in the presence of classic symptoms of diabetes such as polydipsia, polyphagia, polyuria, and blurred vision is diagnostic of diabetes mellitus at any age. Oral Glucose Tolerance Test. The OGTT is an impor- tant screening test for diabetes. The test measures the body’s ability to store glucose by removing it from the blood. In men and women, the test measures the plasma glucose response to 75 g of concentrated glucose solu- tion at selected intervals, usually 1 and 2 hours. In peo- ple with normal glucose tolerance, blood glucose levels return to normal within 2 to 3 hours after ingestion of a glucose load. Because people with diabetes lack the ability to respond to an increase in blood glucose by