Diabetes mellitus type 2 overview

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Differentiating Diabetes Mellitus Type 2 from other Diseases
Epidemiology and Demographics
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Diabetes mellitus Main page
Patient Information Type 1 Type 2
Overview
Classification Diabetes mellitus type 1 Diabetes mellitus type 2 Gestational diabetes
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Complications
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Prevention

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Priyamvada Singh, M.B.B.S. [2]; Cafer Zorkun, M.D., Ph.D. [3]; Tarek Nafee, M.D. [4]

Overview

Diabetes mellitus type 2 (formerly called non insulin-dependent diabetes (NIDDM), obesity related diabetes, or adult-onset diabetes) is a metabolic disorder that is primarily characterized by insulin resistance, relative insulin deficiency, and hyperglycemia. The defective responsiveness of body tissues to insulin almost certainly involves the insulin receptor in cell membranes. In the early stage the predominant abnormality is reduced insulin sensitivity, characterized by elevated levels of insulin in the blood. At this stage hyperglycemia can be managed by engaging in exercise, modifying one's diet and medications that improve insulin sensitivity or reduce glucose production by the liver. As the disease progresses the impairment of insulin secretion worsens, and therapeutic replacement of insulin often becomes necessary. It is rapidly increasing in the developed world, and there is some evidence that this pattern will be followed in much of the rest of the world in coming years. The CDC has characterized the increase as an epidemic.

Historical Perspective

Diabetes mellitus is a well-recognized disease from ancient times. In 1812 diabetes mellitus became a recognized clinical entity in The New England Journal of Medicine and Surgery. In 1889, the pancreas was identified as playing a major role in the pathogenesis of the disease. The discovery of insulin in 1921 was a major turning point in the history of diabetes when Frederick Banting and Charles Best were able to reverse the diabetic state in dogs by injecting pancreatic isolate from healthy dogs.

Pathophysiology

The exact pathophysiology of type 2 diabetes mellitus is not fully understood. The underlying pathology is the development of insulin resistance. Contrary to type 1 diabetes, patients with type 2 diabetes sufficiently produce insulin; however, cellular response to the circulating insulin is diminished. The mechanism by which the insulin resistance develops is postulated to be influenced by both genetic and environmental factors. Environmental influences on the pathogenesis of type 2 DM include high glycemic diets, central obesity, older age, male gender, low-fiber diet, and high saturated fat diet.

Causes

The underlying cause of type 2 diabetes is insulin resistance. The exact cacuse of insulin resistance is not known, however several theories exist. Central obesity, aging, and high glycemic diets are most commonly implicated in the development of type 2 diabetes.

Differentiating Diabetes mellitus type 2 from other Diseases

Type 2 diabetes mellitus must be differentiated from other disorders that may present with polyuria, polydipsia, weight loss or weight gain. Such disorders may include other forms of diabetes mellitus (e.g. type 1 DM, MODY) or other endocrine disorders (e.g. hypothyroidism, cushings syndrome, wolfram syndrome, alstrom syndrome) or drug

Epidemiology and Demographics

The prevalence of type 2 diabetes mellitus (DM) is well studied in the United States and other developed countries. However, worldwide there is a large variation in the results of the population studies in developing countries and particularly in rural areas with poor access to healthcare. For this reason, diabetes is estimated to be undiagnosed in approximately 50% of adults worldwide. In the United States, African Americans, Mexican Americans, American Indians and non-Hispanic blacks are at a higher risk of developing type 2 diabetes compared to non-Hispanic whites. It is more prevalent among those older than 65 years, although there is a growing tend of childhood-onset of the disease. In 2011, 335 million people were estimated to have type 2 diabetes and that number is on a trajectory to reach over 500 million people by 2050. These figures correlate with a prevalence of approximately 5000 and 7500 per 100,000 in 2011 and 2050, respectively. Type 2 diabetes is more prevalent among men than women and in countries with low to mid income levels compared to high income level countries. It is classified as a global epidemic that is growing in parallel to massive urbanization.