What is carcinoid syndrome?

Some neuroendocrine tumours (NETs) make large amounts of hormones and proteins. The most common substance they make is serotonin. 

Serotonin and the other proteins are released into the bloodstream and this can cause a collection of symptoms called carcinoid syndrome.

Carcinoid syndrome is common in people with a small bowel NET that has spread to the liver. More than 9 out of every 10 people (more than 90%) whose small bowel NET has spread to their liver have carcinoid syndrome.

Carcinoid syndrome can also happen in people with lung and pancreatic NETs. But this is rare.


The main symptoms of carcinoid syndrome are: 

Flushing of the skin

The skin of your face, neck and chest might look red (flushed). It may also feel warm and itchy.

More than 8 out of every 10 people (more than 80%) with carcinoid syndrome have this symptom.

Flushing of the skin is often unexpected and unpredictable. Some people find that it is triggered by certain foods, drinking coffee or alcohol, stress or exercise.


Diarrhoea means having more than 3 watery poos (stools) in a 24 hour period. This can be severe, some people with carcinoid syndrome have diarrhoea more than 15 times a day. 

More than 7 out of every 10 people (more than 70%) with carcinoid syndrome have diarrhoea.

Other symptoms

Other symptoms of carcinoid syndrome include:

  • tummy (abdominal) pain
  • fast heartbeat (palpitations)
  • red spidery marks on your skin (telangiectasia) caused by small broken blood vessels
  • a build up of fluid in your legs and ankles
  • a whistling sound when breathing (wheezing)


You usually have tests to diagnose carcinoid syndrome. This helps your doctor plan your treatment. The tests you might have include:

Blood tests can check your general health. It can also check the amount of a protein called chromogranin A. This is usually higher than normal when you have carcinoid syndrome.

Serotonin is broken down into a substance called 5-HIAA. Your doctor can test for this in your wee (urine) or you might have this as a blood test. 

To measure the amount of 5-HIAA in your urine, your doctor or nurse asks you to collect all your urine over 24 hours. 

A CT scan can show up whether the NET has spread to the liver.

These are octreotide scans (or octreoscans) and MIBG scans. You have an injection of a low dose radioactive substance, which is taken up by some NET cells. The cells then show up on the scan.

You might have other tests to look for the NET, its size and whether it has spread.

You can find out more about the tests you might have to diagnose a NET in the getting diagnosed pages for your NET type.


The main aim of treatment is to reduce your symptoms. This means reducing the amount of hormones and proteins the NET is making. This won’t get rid of the NET but can control your symptoms and help you feel better. 

Treatment you might have includes:


Most people with carcinoid syndrome have tumour spread in the liver. Your doctor might suggest you have surgery to remove some of the liver tumour. This might help with your symptoms. 

The type of surgery you have depends on where the tumour is and its size. You usually have liver surgery at the same time you have surgery to remove the tumour where the NET started (primary cancer).

Somatostatin analogues

Somatostatin is a protein made naturally in the body. It does several things including slowing down the production of hormones. Somatostatin analogues are man made versions of somatostatin.

You may have somatostatin analogues to try to slow down the tumour and help with symptoms. They include: 

  • octreotide (Sandostatin)
  • lanreotide (Somatuline)

Interferon alfa

Interferon is a drug that stimulates the body’s immune system to attack the NET. It helps to control the symptoms and can slow down the growth of the tumour.

You might have interferon alfa on its own, or with a somatostatin analogue. 


Rarely, people with carcinoid syndrome may develop other complications such as carcinoid heart disease and carcinoid crisis. 

Your doctor regularly checks for these.

Last reviewed: 
22 Mar 2021
Next review due: 
22 Mar 2024
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  • The information on this page is based on literature searches and specialist checking. We used many references and there are too many to list here. Please contact patientinformation@cancer.org.uk with details of the particular issue you are interested in if you need additional references for this information.

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