Introduction to Diabetes

Rita Rastogi Kalyani, M.D., M.H.S.

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 30.3 million people, or 9.4% of the U.S. population, had diabetes in 2015 and one-third of U.S. adults 18 years or older had prediabetes[11]. 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. is projected to continue exponentially increasing to 54.9 million in 2030[2].
  • Diabetes is the seventh leading cause of death in the U.S.[12]
  • The total estimated cost of diagnosed diabetes in 2017 was $327 billion.[1]
  • 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 up to 5% of cases; and other types (i.e. unusual genetic forms) can occur but are more rare. 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: June 2, 2018