diabetes mellitus

diabetes mellitus
Field	Endocrinology

diabetes mellitus. It is a group of metabolic disorders characterized by persistent high blood sugar levels, known as hyperglycemia. This condition results from defects in insulin secretion, insulin action, or both, leading to the improper metabolism of carbohydrates, fats, and proteins. The chronic hyperglycemia of diabetes is associated with long-term damage, dysfunction, and failure of various organs, especially the eyes, kidneys, nerves, heart, and blood vessels.

Definition and classification

The World Health Organization and the American Diabetes Association provide widely used diagnostic criteria and classification systems. The main categories include type 1 diabetes, type 2 diabetes, gestational diabetes, and other specific types such as those due to genetic defects or diseases of the exocrine pancreas. Type 1 diabetes is characterized by an absolute deficiency of insulin secretion, often resulting from autoimmune destruction of the beta cells in the islets of Langerhans within the pancreas. In contrast, type 2 diabetes involves a combination of insulin resistance and an inadequate compensatory insulin secretory response.

Signs and symptoms

Classic symptoms include polyuria, polydipsia, unexplained weight loss, and sometimes polyphagia. These result directly from hyperglycemia and the resultant osmotic diuresis. Many individuals with type 2 diabetes may be asymptomatic for years. Other common presentations include blurred vision, fatigue, slow-healing wounds, and recurrent infections such as candidiasis. The presence of acanthosis nigricans can be a cutaneous marker of insulin resistance. Acute, life-threatening complications include diabetic ketoacidosis, more common in type 1 diabetes, and hyperosmolar hyperglycemic state, often seen in type 2 diabetes.

Causes and pathophysiology

The fundamental cause varies by type. Type 1 diabetes is an autoimmune disease where the immune system, influenced by genetic susceptibility and potential environmental triggers like certain viruses, attacks pancreatic beta cells. Type 2 diabetes is primarily driven by insulin resistance, often related to obesity, physical inactivity, and genetic factors, leading to a progressive decline in beta-cell function. Gestational diabetes arises from insulin resistance during pregnancy due to hormonal changes from the placenta. Other causes include diseases of the pancreas like chronic pancreatitis, genetic syndromes such as maturity-onset diabetes of the young, and drug-induced forms from medications like glucocorticoids.

Diagnosis

Diagnosis is based on blood glucose criteria established by the American Diabetes Association. Key tests include a fasting plasma glucose test, a hemoglobin A1c test, or an oral glucose tolerance test. A random plasma glucose test can be diagnostic in the presence of classic symptoms. The hemoglobin A1c test reflects average blood glucose levels over the preceding two to three months and is also used for monitoring glycemic control. Diagnosis of gestational diabetes is typically performed between 24 and 28 weeks of gestation using specific oral glucose tolerance test protocols.

Management

Management aims to normalize blood glucose levels to prevent complications. For all types, it includes medical nutrition therapy and physical activity. Type 1 diabetes requires lifelong insulin administration, delivered via multiple daily injections or an insulin pump. Management of type 2 diabetes may involve oral medications like metformin, sulfonylureas, or newer agents such as SGLT2 inhibitors and GLP-1 receptor agonists, often progressing to insulin therapy. Blood pressure control with agents like ACE inhibitors and lipid management are critical. Regular screening for complications, including retinopathy, nephropathy, and neuropathy, is essential. Technological advances include continuous glucose monitors and automated insulin delivery systems.

Epidemiology

Diabetes is a major global public health issue. According to the International Diabetes Federation, hundreds of millions of adults worldwide are affected, with prevalence rising rapidly. Type 2 diabetes accounts for the majority of cases globally. High prevalence rates are observed in regions like the Pacific Islands, the Middle East, and North America. Significant risk factors include obesity, aging, family history, and ethnicity, with higher rates noted among groups such as African Americans, Hispanic Americans, and South Asians. The economic burden on healthcare systems, including those of the National Health Service in the United Kingdom and Medicare in the United States, is substantial.

History and society

The disease was first described in ancient Egyptian manuscripts from the Ebers Papyrus. The term "diabetes" was coined by the Greek physician Aretaeus of Cappadocia. In the 17th century, Thomas Willis noted the sweet taste of urine, leading to the full name *diabetes mellitus*. A pivotal moment was the discovery of insulin in 1921 by Frederick Banting and Charles Best at the University of Toronto, a breakthrough for which Banting and John Macleod received the Nobel Prize in Physiology or Medicine. Cultural depictions exist, such as in the works of H.G. Wells. Major advocacy and research organizations include the Juvenile Diabetes Research Foundation and Diabetes UK. World Diabetes Day, led by the International Diabetes Federation, is observed annually on November 14th.

Category:Endocrine diseases Category:Metabolic disorders