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For Clinicians

Octreotide Case 4 Answers

1) Any evidence for metastases?

There are innumerable liver metastases

2) Explain the normal 5HIAA

5-HT (serotonin) is produced by carcinoid tumours. 5HIAA is a breakdown product of 5HT and is excreted in the urine and elevated levels can therefore be detected. If the tumour is confined to that which is drained by the portal circulation, the patient is often asymptomatic and the 5HIAA levels are not hugely elevated. With liver metastases or extrahepatic carcinoid, 5-HT levels are elevated and thought to be responsible for the majority of the symptoms suffered in the carcinoid syndrome (flushing, bronchoconstriction, diarrhoea, right heart failure due to stenosis of the tricuspid and pulmonary valves). Various other neuropeptides entering the systemic circulation such as bradykinin are thought to have a role in symptomatology as 20% of those with proven serotonin-secreting tumours fail to develop carcinoid syndrome.

Only 3-5% of patients with a carcinoid syndrome will develop the carcinoid tumour. Of these 70-90% have midgut tumours with liver metastases. Some carcinoid tumours, particularly foregut carcinoids, may lack the enzymes to produce 5-HT and thus no excess 5HIAA is produced, as in this case

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