1. The symptoms of episodic hypoglycaemia may be suggestive of CNS disease, hysteria, epilepsy, sympathetic overactivity, behavioural problems, or intoxication. Patients may complain of sweating, hunger, palpitations, or exhibit various focal neurological deficits coinciding with cerebral hypoglycaemia. Symptoms are either spontaneous, or induced by an overnight fast, or a controlled insulin infusion.They frequently occur before breakfast, or during vigorous exercise. In a study of 25 patients, the median time of severe symptoms of cerebral hypoglycaemia was 2 years and one-third of patients had had hypoglycaemic seizures (Doherty et al 1991). Hypoglycaemia may also occur in pregnancy or postpartum. One patient was found to be comatose on the second morning after delivery (Garner & Tsang 1989). Another was found confused, hypothermic (31.3°C), and sweating at 33 weeks' gestation, with a blood sugar of 0.8 mmol l-1. Difficulty was experienced maintaining her blood sugar because she had very high insulin levels. On CT scan she had low-density defects throughout the liver parenchyma, suggesting nonislet cell hypersecretion of insulin (Hyer et al 1995).
2. The diagnostic criteria for insulinomas i include a fasting plasma insulin of >6 |m Uml-1 | and detectable levels of serum C-peptide, at the same times as symptoms of hypoglycaemia and a blood glucose concentration of <2.5 mmol l-1 (Le Roith 1999). Closely supervised fasts of up to 24 h or beyond may be required, since factitious hypoglycaemia has been produced by concealed consumption of oral hypoglycaemics (Proye et al 1998).
3. Medical control of insulin secretion may be required for those in whom tumours cannot be localised, or who are unfit for surgery (Gill et al 1997). Diazoxide probably counteracts hypoglycaemia by effects on beta-cell potassium channels, but may cause fluid retention. The somatostatin analogue octreotide, or streptozotocin, may also be used.
4. A small percentage of insulinomas form part of a multiple endocrine neoplasia syndrome
5. Diagnosis may be difficult. Ultrasound and CT scans are not very sensitive. MRI angiography, selective visceral angiography, or portal venous sampling, may be required (Geoghegan et al 1994).
Was this article helpful?