Hypoglycaemia
Hypoglycaemia is defined as a plasma glucose<2.5 mmol/L. The actual glucose level at which symptoms develop varies markedly.
Symptoms and Signs
The most common symptoms include sweatiness, palpitations, weakness, hunger, drowsiness, restlessness, tremor, seizures and coma. Occasionally personality changes may be a presenting symptom. By far the most common cause of hypoglycaemia is an excess of insulin or oral hypoglycaemic agents in a known diabetic. Enquire about a history of diabetes mellitus and medication. Occasionally relatives of diabetics may be covertly ingesting hypoglycaemic agents. Insulin has been used by athletes to improve stamina. Alcohol excess without food may lead to hypoglycaemia. A full medication history is important.
There may be a history of pituitary dysfunction. Causes of pituitary failure include tumour, trauma, pituitary surgery and infection. The symptoms of Addison’s disease include weakness, weight loss, dizziness and pigmentation of the buccal mucosa and palmar creases. Islet cell tumours may produce symptoms of hypoglycaemia intermittently and to varying degrees. Classically, the symptoms develop during fasting. Personality or neurocognitive changes may develop. Diagnosis of insulinoma depends on the classical diagnostic triad, i.e. Whipple’s triad: (1) attacks precipitated by fasting; (2) blood sugar is low during the attack; (3) symptoms are relieved by administration of glucose. Check for a history of liver failure. Dumping syndrome may occur following gastric surgery when a high osmotic load is delivered to the jejunum. A history of lymphoma may be present in immune-mediated hypoglycaemia.
Examination may reveal classic signs of hypoglycaemia. Look for complications of diabetes. Look for evidence of chronic liver disease in alcoholics. Pituitary insufficiency may lead to a variety of examination findings depending upon the deficiency and may include hypotension, loss or gain of weight, breast atrophy, hypogonadism, weakness, central obesity or dry skin. Retroperitoneal tumours may lead to renal impairment. Look for features of chronic liver disease. Lymphadenopathy and hepatosplenomegaly may be apparent in Hodgkin’s disease.
Investigations
■ LFTs
↑ bilirubin and transaminases with liver failure.
■ U&Es
↑ urea and creatinine with renal failure associated with retroperitoneal disease.
■ Insulin and C-peptide levels
Normal or ↑ insulin (insulinoma, sulfonylurea treatment). Absent C-peptide with exogenous insulin.↓insulin (non-pancreatic neoplasm, insulin receptor antibodies), alcohol, pituitary or adrenal failure.
■ Pituitary hormone levels
Reduced in pituitary failure (e.g. GH (growth hormone), TSH, LH, FSH, prolactin).
■ Prolonged oral glucose tolerance test
To identify dumping syndrome.
■ i.v. insulin suppression test
Insulinoma.
