What is carcinoid syndrome?

Carcinoid syndrome includes many symptoms seen in people with rare tumors. Carcinoid tumors are slow-growing and usually form in the gut. It is when they spread to the liver that the symptoms in this syndrome are caused.

This article will explore how carcinoid syndrome develops, who is at risk, and what can be done to treat it.

Types of Carcinoid Syndrome

Carcinoid syndrome is a term used to describe the symptoms that occur when carcinoid tumors trigger the release of too much serotonin and other chemicals into the bloodstream. It occurs in about 10 percent of people with carcinoid tumors, and usually only after the tumor has spread from its original location to the liver or lungs.

Carcinoids are rare tumors that develop from neuroendocrine cells that send and receive messages throughout the body. Since neuroendocrine cells can be found in nearly every tissue in the body, you can develop these tumors anywhere.

However, carcinoid tumors often start in the appendix or lungs in children, and the gastrointestinal (GI) tract in adults. Carcinoid tumors grow slowly and can spread to other organs in children and adults, but metastases — secondary cancerous growths in other parts of the body — are more common in adults with the disease.

Common sites of origin for carcinoid tumors include:

  • small intestine
  • appendix
  • rectum
  • lung
  • colon
  • Stomach
  • pancreas

by number

Carcinoid tumors are so rare that only about 4 in 100,000 adults are diagnosed, and only 10% of them go on to develop carcinoid syndrome. Many people with carcinoid tumors have no symptoms at all.

carcinoid syndrome symptoms

It is possible to develop carcinoid tumors without ever showing symptoms, but 10% of people with carcinoid tumors develop carcinoid syndrome.

Carcinoid syndrome is defined by the symptoms it causes. These symptoms are often signs of abnormal hormone secretion and signals from carcinoid tumors and neuroendocrine cell dysfunction. Symptoms usually appear later in the disease.

The most common symptoms of carcinoid syndrome are:

  • Flushing or redness of the face, neck, and upper chest
  • Breathing problems such as wheezing
  • diarrhea
  • cardiovascular problems, such as damaged heart valves

Symptoms may also include:

  • weight change
  • malnutrition
  • weakness
  • Muscle pain
  • joint pain
  • peptic ulcers (open sores in the upper stomach and small intestine)

Carcinoid tumors: signs, symptoms, and complications


Carcinoid syndrome is essentially an advanced stage of carcinoid tumors that have metastasized to multiple parts of the body. At this point, these tumors begin to interfere with the body’s hormonal balance and other signals that affect function.

Experts aren’t sure why people develop carcinoids, perhaps because they’re so rare. There are several factors that seem to indicate a higher risk of developing these tumors. These include:

  • smokes
  • bad eating habits
  • African American
  • family history of cancer
  • certain genetic diseases
  • increasing age


In some people, carcinoid syndrome can be difficult to diagnose — especially if you have no previous symptoms of carcinoid tumors. Most carcinoid tumors are completely asymptomatic and are often discovered incidentally, such as during surgery for another disease.

If you start to experience any of the four main symptoms listed above — especially if you’re one of the high-risk groups — it’s best to make an appointment with your healthcare provider. See your doctor right away if you can’t breathe or start to have symptoms of heart problems.

Your healthcare provider will usually begin the exam by taking your personal and family medical history, looking for any red flags that may indicate the cause of your symptoms. An accurate diagnosis is usually made after many tests, which may include:

  • blood test
  • Imaging studies, such as a CT (computed tomography) scan or MRI (magnetic resonance imaging) of the chest or abdomen
  • 5-Hydroxyindoleacetic acid (5-HIAA) detection in urine
  • an echocardiogram (to examine how blood is pumped through the heart’s chambers and valves)
  • A new generation of PET (Positron Emission Tomography) scans called PET-DOTATATE

These tests can detect carcinoid tumors, which may help your healthcare provider interpret the symptoms you might experience in carcinoid syndrome.

How to Diagnose Carcinoids


The main treatment for carcinoid syndrome is to first remove the tumor that causes the disease. Many times, this means surgery to remove or reduce the size of the carcinoid tumor.

Other treatment options, especially when surgery is not an option, include:

  • Sandostatin (octreotide) or Somatuline (lanreotide) injections: These are synthetic versions of somatostatin, a natural hormone produced by the body.
  • Chemotherapy: Often used in cancer treatment, chemotherapy can also target carcinoid tumor cells.
  • Targeted therapy: Biological drugs such as Afinitor (everolimus) work by regulating cell growth and significantly slowing the progression of carcinoid tumors.
  • Peptide receptor radionuclide therapy (PRRT): This therapy directs high-energy radiation to tumor cells to destroy or slow their growth while reducing harmful effects on healthy tissue.

How to treat carcinoid tumors


The prognosis of patients with carcinoid syndrome depends largely on the location and extent of the carcinoid tumor. The outcome of carcinoid syndrome is usually good, not fatal.

Carcinoid syndrome and underlying neuroendocrine tumors may cause complications. These include:

  • Low blood pressure leads to increased falls
  • intestinal obstruction
  • Gastrointestinal bleeding
  • heart valve problems or failure

What is carcinoid?


The symptoms of carcinoid syndrome can be difficult to manage, especially if they cause severe low or high blood pressure, or other problems that can affect your ability to function during a normal day.

Early detection and treatment of tumors can help prevent carcinoid syndrome, and even if you have a carcinoid tumor, there are a number of strategies you can use to keep the condition from getting worse.

Some tips for managing carcinoid tumors and carcinoid syndrome include:

  • maintain a healthy high-protein diet
  • Avoid alcohol and other substances that may trigger symptoms
  • quit smoking
  • relieve pressure
  • Join a support group

How to Support Relatives and Friends with Cancer


Carcinoid syndrome is caused by carcinoid tumors—usually a more advanced stage tumor. You may not know you have a carcinoid tumor, such as those seen in carcinoid syndrome, until you have severe symptoms. Talk to your healthcare provider if you experience any of the risk factors for carcinoid syndrome, or if you are diagnosed with carcinoid and start to feel worse.

VigorTip words

Carcinoid tumors are rare tumors that can affect hormonal balance and cause a range of other problems, such as flushing of the face, fluctuations in blood pressure, and even changes in heart rate. These tumors usually have no symptoms at all, but once they have spread to your body, they can develop into carcinoid syndrome. If you develop signs or symptoms of carcinoid syndrome, seek help from a medical professional to determine if you have a carcinoid tumor.