DIABETES

Diabetes



Diabetes

Introduction

Diabetes is a group of chronic metabolic diseases characterized by hyperglycemia due to a defect in insulin secretion, insulin action, or both. Diabetes mellitus increases morbidity, mortality, and health care costs through acute and chronic complications, including ketoacidosis, hyperosmolarity, cardiovascular disease, kidney disease, retinopathy, neuropathy, and limb amputations.

The prevalence of diabetes increases with age. Approximately 8.7% of American adults are affected by diabetes mellitus, and most develop type 2 diabetes mellitus (T2DM). In the past two decades, the world has witnessed an alarming increase in the prevalence of diabetes. From 1985 to 2000, the worldwide prevalence of diabetes in adults rose from 30 million to 150 million. By 2025, the figure is expected to reach nearly 330 million (International Diabetes Federation [IDF], 2003). According to the IDF (2003), while the prevalence of diabetes is currently higher in developed countries than it is in developing countries, this trend is changing. Western and urban influences have increased aging populations, unhealthy diets, obesity, and sedentary lifestyles in developing countries, which has led to a staggering rise in the prevalence of diabetes in these areas.

Classification, Etiology, and Pathogenesis

In addition to the two major types of diabetes (type 1 diabetes mellitus [T1DM] and T2DM), rarer types of diabetes include gestational diabetes, diabetes due to medications (e.g., glucocorticoids), and secondary diabetes due to diseases of the exocrine pancreas (e.g., infections, cancer). T1DM, formerly termed insulin-dependent diabetes mellitus or juvenile diabetes, is caused by the autoimmune destruction of the pancreatic ß-cells, leading to absolute insulin deficiency. Both genetic predisposition and environmental factors such as infections are important in the pathogenesis of T1DM. In fact, concordance rates for T1DM are only approximately 50% in monozygotic (identical) twins. T1DM most commonly develops during childhood or adolescence and is the prevalent type of diabetes mellitus diagnosed before 30 years of age. T1DM accounts for 5% to 10% of diabetes and is clinically distinguished by sudden onset, severe hyperglycemia, and a susceptibility to develop diabetic ketoacidosis (DKA).

T2DM, formerly called non-insulin-dependent diabetes mellitus or adult diabetes, usually develops over a prolonged period in stages, beginning with insulin resistance that requires an increase in insulin secretion to maintain normoglycemia. Over time, progressive ß-cell dysfunction in predisposed individuals occurs, leading to impaired glucose tolerance. Progressive pancreatic ß-cell failure and increased insulin resistance ultimately lead to T2DM. Genetic predisposition is very important for the development of T2DM because the concordance between identical twins is ...