Updated 14 December 2016

Carcinoid syndrome

A typical collection of symptoms caused by a carcinoid tumour.



A typical collection of symptoms caused by a carcinoid tumour.

Alternative names

Argentaffinoma Syndrome.

What is this?

Symptoms and problems caused by the secretion of large amounts of various chemicals by a specific carcinoid tumour (also called an argentaffinoma ).

What causes this?

Carcinoid tumours may arise in the bronchial tubes of the lung, in the colon, small intestine, or the gut. They secrete large amounts of serotonin, as well as other chemicals. They tend to produce dilation of the blood vessels, and tend to cause wheezing and diarrhoea. Normally, a substance in the diet called tryptophan is a basis for making the vitamin niacin, and other proteins. But in carcinoid syndrome, it is mainly converted into serotonin, which is itself then eventually changed into a chemical called 5-HIAA. The chemicals may also cause clotting by causing the blood's platelets to clump together.

What are its symptoms?

Symptoms may vary, as the nature of the chemicals the tumour secretes varies, and may include prostaglandins and histamine. Typical symptoms, which often occur in attacks lasting minutes or even days, are bright red flushing of the face, perhaps wheezing, and sudden, severe and explosive diarrhoea, with abdominal cramps. There may be abdominal pain, palpitations, and low blood pressure, perhaps some facial swelling. Heart problems may develop, including damage to the tricuspid or pulmonary heart valves.

How is it diagnosed?

A urine test of a sample collected over 24 hours usually shows much higher levels of 5-HIAA. Before the test, one has to abstain from foods and medications which would raise these levels and produce an unreliable result, including bananas, pineapples, plums, tomatoes, kiwi fruit, paracetamol, some antidepressants and anti-psychotic drugs, and caffeine being the most important ones. Other blood tests and scans may be used too.

How is it treated?

Surgery is the primary treatment, seeking to remove the entire tumour. Even where for some reason total removal isn't practical, removing much of it can be very helpful. Where surgery is difficult, injections of sandostatin (octreotide) and interferon, may be useful, as part of chemotherapy. A serotonin antagonist can control the diarrhoea. Caution is needed about using other drugs such as those antidepressants which increase the impact of serotonin.

What is the prognosis?

Variable, depending on a number of factors concerning the tumour itself, and how early on in its development it is discovered and treated. Among possible complications is right-sided heart failure. Locating the tumour can be difficult, though isotope scans can help, and a laparotomy (an operation to explore the abdomen) may be needed to search for it. Where the tumour is well localised, there can be a 95% 5-year survival, falling to around 20% where the tumour has spread to the liver.

When to call your doctor

If you experience typical attacks including severe flushing, and diarrhoea.

How can it be prevented?

Sometimes the tumours are discovered before they have caused any symptoms, during an abdominal operation for some other reason.


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