Porth's Essentials of Pathophysiology, 4e

818

Endocrine System

U N I T 9

blood glucose levels also may impair host defenses such as the function of neutrophils and immune cells. Polymorphonuclear leukocyte function, particularly adherence, chemotaxis, and phagocytosis, is depressed in persons with diabetes, particularly those with poor glycemic control.

R E V I EW E X E R C I S E S 1. A 6-year-old boy is admitted to the emergency department with nausea, vomiting, and abdominal pain. He is very lethargic; his skin is warm, dry, and flushed; his pulse is rapid; and he has a sweet smell to his breath. His parents relate that he has been very thirsty during the past several weeks, his appetite has been poor, and he has been urinating frequently. His initial plasma glucose is 420 mg/dL (23.1 mmol/L), and a urine test for ketones is strongly positive. A. What is the most likely cause of this boy’s elevated blood glucose and ketonuria? B. Explain his presenting signs and symptoms in terms of the elevated blood glucose and metabolic acidosis. C. What type of treatment will this boy require? 2. A 53-year-old accountant presents for his routine yearly examination. His history indicates that on two prior occasions he had a fasting plasma glucose of 120 mg/dL (6.7 mmol/L). Currently he is asymptomatic. He has no other medical problems and does not use any medications. He neither smokes nor drinks alcohol. His father was diagnosed with type 2 diabetes at age 60 years. His physical examination reveals a blood pressure of 125/80 mm Hg, ■■ Pharmacologic agents used in the management of diabetes include injectable insulin, injectable non-insulin agents including amylin and GLP-1 analogs, and oral diabetic drugs.Type 1 diabetes (and sometimes type 2 diabetes) requires treatment with injectable insulin. Oral antidiabetic drugs include the insulin secretagogues, biguanides, α -glucosidase inhibitors, thiazolidinediones, and incretin-based therapies. These drugs require a functioning pancreas and may be used in the treatment of type 2 diabetes. ■■ The metabolic disturbances associated with diabetes affect almost every body system.The acute complications of diabetes include diabetic ketoacidosis, hyperglycemic hyperosmolar state, and hypoglycemia in people with insulin-treated diabetes.The chronic complications of diabetes affect the microvascular system (including the retina, kidneys, and peripheral nervous system) and the macrovascular system (coronary, cerebrovascular, and peripheral arteries).The diabetic foot is usually a combination of both microvascular and macrovascular dysfunction. Infection is also a frequent occurrence and is more likely to be severe in the diabetic patient.

SUMMARY CONCEPTS

■■ Diabetes mellitus is a disorder of carbohydrate, protein, and fat metabolism resulting from an imbalance between insulin availability and insulin need. In type 1 diabetes, there is destruction of beta cells and an absolute insulin deficiency.Type 2 diabetes is characterized by a lack of insulin availability or effectiveness. Diabetes can also occur secondary to some other condition that destroys beta cells (e.g., pancreatic disorders) or endocrine diseases that cause increased production of glucose by the liver and decreased use of glucose by the tissues (e.g., Cushing syndrome). Gestational diabetes develops during pregnancy. ■■ The metabolic syndrome represents a constellation of metabolic abnormalities characterized by obesity, insulin resistance, high triglyceride levels and low HDL levels, hypertension, cardiovascular disease, and increased risk for development of type 2 diabetes. ■■ The most commonly identified symptoms of type 1 diabetes are polyuria, polydipsia, polyphagia, and weight loss despite normal or increased appetite. Although persons with type 2 diabetes may present with one or more of these symptoms, they are often asymptomatic initially. The diagnosis of diabetes mellitus is based on clinical signs of the disease, fasting blood glucose levels, random plasma glucose measurements, and results of the glucose tolerance test. Glycosylation involves the irreversible attachment of glucose to the hemoglobin molecule; the measurement of glycosylated hemoglobin (A1C) provides an index of blood glucose levels over several months. Self-monitoring of capillary blood glucose provides a means of maintaining near-normal blood glucose levels through adjustment of insulin dosage. ■■ Dietary management of diabetes focuses on maintaining a well-balanced diet, controlling calories to achieve and maintain an optimum weight, and regulating the distribution of carbohydrates, proteins, and fats.