Definition
Diabetes mellitus (DM) is a chronic metabolic disorder characterized by hyperglycemia due to a deficiency of insulin secretion, insulin action, or both. It leads to disturbances in the metabolism of carbohydrates, fats, and proteins.
Pathogenesis
Type 1 DM (T1DM)
- T-cell-mediated autoimmune destruction of β-cells → ↓ insulin production.
- Often triggered in genetically predisposed individuals by environmental factors (e.g., viral infections like coxsackie B).
- Insulin deficiency leads to increased lipolysis, ketone production → risk of diabetic ketoacidosis (DKA).
Type 2 DM (T2DM)
- Insulin resistance (↓ cellular response to insulin) + β-cell dysfunction.
- Obesity (especially visceral) plays a major role by secreting inflammatory cytokines → worsens insulin resistance.
- Initially compensated by ↑ insulin secretion, but later β-cell exhaustion leads to hyperglycemia.
Clinical Features
T1DM (often acute onset in youth)
- Polyuria, Polydipsia, Polyphagia
- Weight loss despite increased appetite
- Fatigue
- Acetone breath (from ketosis)
- DKA in severe cases
T2DM (often insidious in adults)
- Gradual onset
- Fatigue, blurred vision, poor wound healing
- Recurrent infections
- May be asymptomatic, discovered incidentally via routine labs