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:

e.g:

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)

Note:

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.