Diabetes Mellitus: Etiology and Epidemiology

Diabetes mellitus is a chronic metabolic disorder characterized by hyperglycemia and is associated with microvascular and macrovascular complications. Diabetes is the leading cause of noncommunicable diseases worldwide and has reached epidemic proportions in certain parts of the world and in certain ethnic groups. Type 1 diabetes (T1D) is due to autoimmune destruction of insulin-secreting pancreatic β -cells of islets of Langerhans. Type 2 diabetes (T2D) is a multifactorial disease with genetic and environmental factors (especially those causing obesity) playing a key role in its pathogenesis. T2D is the most common form of diabetes worldwide accounting for 90% of cases globally and affecting approximately 4% of the world's adult population. Both T1D and T2D are distinct from ‘other causes of diabetes’ as defined by the etiological classification of the World Health Organization (WHO), which include maturity onset diabetes of the young (MODY) and fibrocalculous pancreatic diabetes (FCPD). Gestational diabetes (GDM) is the fourth category defined by the s WHO.