Mellitus

Mellitus, in the term diabetes mellitus, refers to a group of metabolic disorders characterized by chronic hyperglycemia. The word mellitus comes from Latin and means honey-sweet, a nod to historical observations of sweet-tasting urine in affected individuals. The condition is distinguished from diabetes insipidus, which involves polyuria not associated with elevated blood glucose.

Most cases of diabetes mellitus are caused by impaired insulin secretion or action. Type 1 diabetes results from autoimmune destruction of pancreatic beta cells, leading to absolute insulin deficiency. Type 2 diabetes arises from a combination of insulin resistance and relatively insufficient insulin production. Other forms include gestational diabetes that occurs during pregnancy and various monogenic or secondary causes such as endocrine disorders or drug-induced diabetes. The condition is commonly associated with obesity and sedentary lifestyle, but genetic and environmental factors also play roles.

Clinical features typically include excessive urination, extreme thirst, unexplained weight loss, fatigue, and sometimes blurred vision or infections. Diagnosis is based on plasma glucose measurements or glycated hemoglobin (HbA1c): fasting plasma glucose of 126 mg/dL (7.0 mmol/L) or higher, a 2-hour glucose of 200 mg/dL (11.1 mmol/L) after an oral glucose tolerance test, HbA1c of 6.5% or higher, or a random glucose of 200 mg/dL (11.1 mmol/L) with classic symptoms.

Management focuses on maintaining near-normal blood glucose levels to prevent complications and typically involves lifestyle changes, regular monitoring, and pharmacotherapy. Type 1 diabetes requires insulin therapy; type 2 diabetes is managed with lifestyle, oral glucose-lowering agents such as metformin, and may progress to insulin. Gestational diabetes is treated to protect both mother and fetus.

Long-term complications can be microvascular (retinopathy, nephropathy, neuropathy) and macrovascular (cardiovascular disease). Early diagnosis and sustained glycemic control are central to reducing morbidity and mortality.