Endocrine and metabolic emergencies: hypoglycaemia.

Hypoglycaemia is rare in healthy individuals owing to the numerous elegant hormonal and neuronal mechanisms that maintain glucose homeostasis. Glucose is an obligate metabolic fuel for cerebral tissue and therefore hypoglycaemia, if uncorrected, can have disastrous consequences including death. Clinical hypoglycaemia is defined as a plasma (or serum) glucose concentration low enough to cause symptoms and/or signs, including impairment of brain function. However, no single plasma (or serum) glucose concentration categorically defines hypoglycaemia. Hypoglycaemia is probably the most common endocrine and metabolic emergency in clinical practice. The overwhelming majority of occurrences of hypoglycaemia occur in patients with diabetes, either as a result of treatment-induced hypoglycaemia and/or abnormalities that affect the normal counterregulatory response to hypoglycaemia. The differential for nondiabetes-associated hypoglycaemia is broad and includes insulinoma, drugs, hormone deficiencies, and critical illness. The acute management of hypoglycaemia is discussed along with a review of the pathophysiology and aetiology of this commonly encountered clinical problem.