Hyperglycemia
Definition
Hyperglycemia is defined as elevated blood glucose levels, typically >7.0 mmol/L (126 mg/dL) fasting, or >11.1 mmol/L (200 mg/dL) random or postprandial.
Classification
Etiology
Diabetes mellitus (most common cause)
- Type 1 DM: autoimmune destruction of β-cells → insulin deficiency.
- Type 2 DM: insulin resistance ± relative insulin deficiency
Other causes
- Endocrine disorders:
- Cushing’s syndrome (↑ cortisol).
- Acromegaly (↑ GH).
- Pheochromocytoma (↑ catecholamines).
- Hyperthyroidism.
- Medications: corticosteroids, thiazides, beta-agonists.
- Severe stress or trauma (stress hyperglycemia).
Pathogenesis
- Decreased insulin secretion or action → reduced cellular glucose uptake.
- Increased gluconeogenesis and glycogenolysis in liver → more glucose release into blood.
- Lipolysis and proteolysis provide substrates for hepatic glucose production.
- Sustained high glucose → osmotic diuresis → dehydration.
Clinical manifestations
- Polyuria (osmotic diuresis).
- Polydipsia (due to dehydration).
- Polyphagia (increased hunger, especially in uncontrolled DM).
- Weight loss (especially in type 1 DM).
- Blurred vision.
- Fatigue, weakness.
- Severe cases: diabetic ketoacidosis (type 1) or hyperosmolar hyperglycemic state (type 2).