Johns Hopkins Diabetes GuideOverview

Introduction to Diabetes

Rita Rastogi Kalyani, M.D., M.H.S., Thomas Donner, M.D., Christopher Saudek, M.D.
Introduction to Diabetes is a topic covered in the Johns Hopkins Diabetes Guide.

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Overview of Diabetes

  • Diabetes mellitus is a common, chronic disease defined by hyperglycemia (high blood glucose), with multiple other metabolic abnormalities (i.e. acidosis) often present.
  • The pathophysiology of diabetes is characterized by relative or absolute insulin insufficiency; in type 1 diabetes the disease results form progressive autoimmune destruction of insulin-producing beta cells; in type 2 diabetes there is both decreased insulin sensitivity and insulin secretory insufficiency.
  • Insulin is the key hormone regulating uptake of glucose from the blood into most cells (primarily skeletal muscle and fat cells). Insulin is released into the blood by beta cells found in pancreatic Islets of Langerhans, in response to rising levels of blood glucose, typically after eating. Insulin also controls conversion of glucose to glycogen for storage in liver and muscle cells. Higher insulin levels increase anabolic processes such as cell growth, protein synthesis, and fat storage. Very low insulin levels result in catabolism and, in particular, can trigger ketosis or breakdown of fat.
  • Diabetes mellitus ("sugar diabetes") is unrelated to diabetes insipidus except that they can both cause polyuria.
  • About 26 million people, or 8.3% of the U.S. population had diabetes in 2011 [3], and over 40% of those >40 years old have either diabetes or pre-diabetes [1]. Of these, approximately a quarter of individuals had undiagnosed diabetes. (See EPIDEMIOLOGY OF TYPE 1 DIABETES and EPIDEMIOLOGY OF TYPE 2 DIABETES
  • The number of people with diabetes in the U.S. will almost double to 44.1 million in the next 25 years [2].
  • Diabetes is the 7th leading cause of death in the U.S., responsible for about 1/3 of expenditures in Medicare
  • Diabetes is the leading cause of: blindness among working age adults (due to diabetic retinopathy and macular edema), non-traumatic amputations, endstage renal disease and dialysis, and peripheral neuropathy.
  • Diagnosis and classification: type 2 diabetes (insulin resistance and relative insulin secretory defect) constitutes 90-95% of cases; type 1 diabetes (absolute insulin deficiency) constitutes 5-10% of cases; and other types (i.e. unusual genetic forms) constitute 1-5% of cases. Gestational diabetes is diabetes that is first diagnosed during pregnancy.
  • Type 2 diabetes is highly associated with increased adiposity, particularly central (abdominal) (See ENVIRONMENTAL RISK FACTORS IN TYPE 2 DIABETES), and positive family history
  • Type 1 diabetes is highly associated with specific genetic markers and is more prevalent in people of northern European ancestry (See RISK FACTORS IN TYPE 1 DIABETES).

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Last updated: July 12, 2013