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Causes of Hyperglycemia

Fasting blood glucose level higher than 126 mg/dl or 7.0 mmol/l is labeled as hyperglycemia.

Fasting hyperglycaemia may occur in the following conditions:

1. Diabetes mellitus:

  –  Absence or insensitivity to insulin, leading to impaired glucose tolerance and hyperglycemia

2. Pancreatic disorders

a.    Pancreatectomy :

–       e.g.: trauma (road traffic accidents,penetrating abdominal injuries), Surgical removal of pancreas (for pancreatic tumor).

b.    Haemochromatosis :

–       Deposition of iron in islets cells within pancreas and destroying islet cells.

c.    Chronic pancreatitis :

–       Chronic inflammation of pancreas resulting in fibrosis & irreversible destruction of pancreatic parenchyma, e.g: Alcohol abuse, longstanding pancreatic duct obstruction.

d.    Carcinoma of pancreas :

–  Glucagonoma  which is the tumour of Islet cells

3. Endocrine disorders

a. Cushing’s syndrome :

–       Glucocorticoids will induce gluconeogenesis and inhibit glucose uptake by tissues causing hyperglycemia.

b.    Acromegaly :

–       Excessive secretion of Growth hormone causes increased gluconeogenesis

c.    Thyrotoxicosis :

–       Causes hyperglycemia by inducing glycogenolysis in liver,also increases the basal metabolic processes (activity/rates).

d.    Phaeochromocytoma :

–       Tumour of adrenal medulla causing hyperglycemia by secretion of catecholamines(epinephrine,norepinephrine),that cause gluconeogenesis.

4. Stress

Increased cortisol and adrenaline secretion leading to gluconeogenesis:


  1. infections
  2. cerebrovascular accidents
  3. myocardial infarction (MI)
5. Iatrogenic

1. IV glucose infusions

2. Drugs

–  Salicylates (analgesics)

– Oral contraceptives(steroid preparation)

– Steroids (used as antiallergic, anti inflammatory, replacement therapy for steroid   deficiency)

-Thiazides (diuretics)


In MI stress, hyperglycaemia is fairly common. However, recent investigations indicate that many of these patients have diabetes mellitus (especially if the plasma glucose exceeds 10 mmol/L); thus, all stress hyperglycaemia patients should be investigated at a later date for possible diabetes mellitus.

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