INSULIN SECRETION, REGULATION, AND THE EPIDEMIOLOGY, CLASSIFICATION, CLINICAL FEATURES, AND DIAGNOSIS OF TYPE 1 AND TYPE 2 DIABETES MELLITUS: A GLOBAL PERSPECTIVE

Diabetes mellitus is a chronic metabolic disorder characterized by persistent hyperglycemia due to defects in insulin secretion, insulin action, or both. Its global prevalence has risen sharply in recent decades, making it a major public health concern. Insulin, produced by pancreatic β-cells, regulates glucose homeostasis through complex mechanisms involving glucose sensing and calcium-mediated secretion. Type 1 diabetes results from autoimmune β-cell destruction and absolute insulin deficiency, whereas type 2 diabetes is characterized by insulin resistance and progressive β-cell dysfunction. Type 2 diabetes accounts for approximately 90–95% of cases worldwide and is strongly linked to obesity and sedentary lifestyle, while type 1 diabetes represents 5–10% of cases. Diagnosis is based on fasting plasma glucose, oral glucose tolerance testing, and HbA1c levels. Early diagnosis, effective management, and preventive strategies are essential to reduce complications and the expanding global burden of diabetes.