type 2 diabetes mellitus

type 2 diabetes mellitus is a chronic metabolic disorder characterized by high blood sugar, insulin resistance, and relative insulin deficiency. It represents the vast majority of diabetes cases globally and is a leading cause of morbidity and mortality. The condition develops over many years and is strongly associated with modifiable lifestyle factors. Management focuses on glycemic control to prevent devastating complications.

Signs and symptoms

Classic symptoms include polyuria, polydipsia, and unexplained weight loss, though many individuals are asymptomatic for years. Hyperglycemia can lead to blurred vision and fatigue. The first presentation is often a complication, such as a recurrent infection like balanitis or candidiasis. Long-term hyperglycemia damages blood vessels, leading to paresthesia in the extremities from diabetic neuropathy and vision changes from diabetic retinopathy. Other presentations may include acanthosis nigricans, a skin condition associated with insulin resistance.

Causes and pathophysiology

The disease arises from a complex interplay of genetics and environmental factors. Key risk factors include obesity, particularly visceral adiposity, and physical inactivity. Genetic susceptibility is polygenic, with notable contributions from loci such as TCF7L2. The pathophysiology involves two primary defects: insulin resistance in tissues like muscle and liver, and progressive beta-cell dysfunction within the pancreatic islets. Insulin resistance leads to increased hepatic glucose production and reduced glucose uptake, while beta-cell failure eventually results in inadequate insulin secretion to compensate.

Diagnosis

Diagnosis is based on blood glucose criteria established by organizations like the American Diabetes Association and the World Health Organization. The primary tests include a fasting plasma glucose of ≥7.0 mmol/L (126 mg/dL), a HbA1c level of ≥6.5% (48 mmol/mol), or a oral glucose tolerance test with a 2-hour value ≥11.1 mmol/L (200 mg/dL). Testing is recommended for individuals with risk factors such as hypertension or a body mass index over 25. The condition is often detected through routine screening before symptoms arise.

Management

The cornerstone of management is lifestyle intervention, including medical nutrition therapy and increased physical activity, often guided by institutions like the National Health Service. First-line pharmacotherapy is typically metformin. If glycemic targets are not met, additional agents are used, such as SGLT2 inhibitors (e.g., empagliflozin), GLP-1 receptor agonists (e.g., liraglutide), or insulin. Management also aggressively addresses cardiovascular risk factors through control of blood pressure with agents like ACE inhibitors and lipid management with statins. Regular screening for complications, including dilated eye examinations and foot care, is essential.

Epidemiology

It is a global pandemic, with prevalence rising sharply. According to the International Diabetes Federation, over 500 million adults were affected worldwide in 2021. High rates are observed in Pacific Island nations and the Middle East. Incidence increases with age and is rising in younger populations due to childhood obesity. Significant disparities exist; in the United States, higher prevalence is seen among African Americans, Hispanic and Latino Americans, and Native Americans. The economic burden on healthcare systems, including Medicare, is substantial.

History

The condition was historically distinguished from other forms by its later onset and lack of dependence on insulin for immediate survival. Ancient physicians like Sushruta and Galen described symptoms consistent with diabetes. The pivotal discovery of insulin by Frederick Banting and Charles Best in the 1920s at the University of Toronto transformed treatment for type 1 diabetes, highlighting the different pathophysiology of the type 2 form. The 20th century saw the development of oral agents, beginning with sulfonylureas introduced in the 1950s and metformin's widespread adoption after the UK Prospective Diabetes Study. Modern drug development continues to evolve, focusing on cardiovascular and renal protection. Category:Diabetes Category:Endocrine diseases