Carcinoid syndrome

Abstract 

Carcinoid tumours are the most common type of neuroendocrine tumour. However, fewer than 10% actually lead to carcinoid syndrome. Carcinoid tumours arise from enterochromaffin and enterochromaffin-like cells, which originate from the primitive gut. Classic symptoms of carcinoid syndrome, such as flushing and diarrhoea, occur as a consequence of the release of hormones, including serotonin, tachykinins and peptide hormones. In the majority of cases, liver metastasis has already occurred at the time of diagnosis. The diagnosis of carcinoid syndrome is made biochemically. Raised levels of a serotonin metabolite, 5-hydroxyindoleacetic acid, are detected during 24-hour urine collection. In addition, raised plasma chromogranin A is supportive of the diagnosis, but is not specific to carcinoid syndrome itself. Somatostatin analogue injections such as octreotide are the mainstay of carcinoid syndrome treatment. Simple therapies such as loperamide and antihistamines may also help to alleviate symptoms. Surgical debulking and hepatic embolization are useful methods to reduce tumour bulk in patients who remain symptomatic on medical treatment. Radioisotope therapy using radiolabelled octreotide or radiolabelled 5-hydroxytryptophan is becoming increasingly available, but is still used in only a minority of cases. A review of the pathophysiology and clinical features of carcinoid syndrome is provided and important issues in its management are highlighted.

Keywords: carcinoid, diarrhoea, flushing, gut, hormone, neuroendocrine, octreotide, serotonin somatostatin, tumour