An Overview of Carcinoid Syndrome

This tumor causes effects throughout the body

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Getting a medical diagnosis

Getty Images/ John Fedele

Carcinoid syndrome is a rare condition characterized by a number of systemic symptoms, including a rapid heart rate, trouble breathing, flushing, and diarrhea. It occurs when a rare type of tumor called a carcinoid tumor produces excess hormones that have effects throughout the body. 

Carcinoid syndrome is diagnosed with blood and urine tests, imaging examinations, and biopsy. The symptoms can be manageable with medication, and resection of the tumor is the most definitive treatment, although complete removal isn’t always possible. 


The signs of carcinoid syndrome typically worsen slowly. The condition may produce severe and rapid effects, but this is less common. The symptoms typically occur after a carcinoid-causing tumor is already diagnosed, but in some instances, carcinoid syndrome can be the first sign of a carcinoid tumor. 

Symptoms include:

  • Flushing
  • Feeling hot 
  • Telangiectasias— pink, reddish or purplish lesions on the face caused by expanded veins 
  • Stomach upset 
  • Diarrhea 
  • Wheezing 
  • Trouble breathing due to airway bronchoconstriction (narrowing)
  • Rapid heart rate 
  • Lightheadedness 
  • Restlessness 

The symptoms may not occur every day, and can come and go. If the diarrhea is severe and lasts for a few days, you can become dehydrated, requiring urgent intravenous (IV) fluid and electrolyte replacement. 

Chronic Effects

After months or years, carcinoid syndrome can lead to carcinoid heart disease and heart failure.

Chronic diarrhea can lead to malnutrition if it prevents you from absorbing the nutrients in the food you eat. This may result in weight loss or major vitamin and mineral deficiencies.


Carcinoid syndrome occurs when a carcinoid tumor produces hormones, particularly serotonin (5-HT). These tumors are also called neuroendocrine tumors because they produce substances that interact with the nervous system and the endocrine system.

The typical locations of carcinoid tumors are the gastrointestinal system or the lungs, although they can occur anywhere in the body. The tumors typically grow in size and may metastasize (spread).

Hormonal Effects

Serotonin, the most prevalent hormone identified in carcinoid syndrome, normally modulates mood. Other hormones that can be produced by these tumors include histamine, kallikrein, prostaglandins, and tachykinins.

These hormones have a variety of actions on the body, including an impact on the blood vessels, heart, and immune system. And experts agree that as many as 40 different hormones could be altered by carcinoid tumors.

The amount of hormone production and the tumor’s systemic effects do not necessarily correspond to its size.


Neuroendocrine tumors can cause a variety of medical problems besides carcinoid syndrome, including weight loss, abdominal pain, abdominal distention (enlarged abdomen), liver failure, pancreatic failure, and coughing up blood. These are all effects of the tumor, and not of carcinoid syndrome.

If you have signs and symptoms of carcinoid syndrome, the next steps in your diagnosis rely on determining whether you have elevated serotonin levels and identifying the tumor. Your doctors will likely do blood and urine tests, as well as imaging tests. 

If you have a carcinoid tumor, your first sign of the illness can be related to carcinoid syndrome or to the effects of the tumor itself.

Blood Tests

Blood tests are often ordered to search for causes of the individual symptoms of carcinoid syndrome, especially if you only have one or a few effects of carcinoid syndrome. For example, if diarrhea is your most prevalent symptom, your doctors will send blood tests to see if you have evidence of an infection (elevated white blood cells) or if the diarrhea may have altered your electrolyte levels (such as sodium and potassium).

When there is a high suspicion that carcinoid syndrome could be the cause of your symptoms, specific tests that are not commonly ordered for other conditions— chromogranin A (CgA), neuron-specific enolase (NSE), cortisol, and substance P, may show evidence of hormone overproduction.

Urine Tests

All hormones, including 5-HT, are metabolized (broken down) before they are eliminated from the body. 5-HT is metabolized into 5-hydroxyindoleactic acid (5-HIAA), which can be detected in the urine. Because 5-HT and 5-HIAA are normally present in the body with or without carcinoid syndrome, urine is collected for 24 hours and the 5-HIAA levels are compared to normal levels.

Imaging Tests

Carcinoid syndrome and carcinoid tumors are evaluated with a number of different imaging tests. If you have symptoms that involve your lungs or gastrointestinal system, imaging examinations such as X-rays, computerized tomography (CT), magnetic resonance imaging (MRI), ultrasound, or positron emission testing (PET) can help your medical team visualize the tumor, and can often detect metastasis as well. 

A specialized imaging test, an octreoscan (somatostatin receptor scintigraphy), involves several steps. First, a radioactive substance that binds to carcinoid tumors is injected. Hours after injection, the substance may bind to cells of carcinoid tumors, which makes the tumors more visible on nuclear imaging tests. Sometimes, this test can help your medical team to see whether there are metastases because the radioactive substance can bind to tumor cells wherever they are located in the body.

Interventional Diagnostic Procedures

There are also diagnostic procedures that can be used to obtain a picture of the inside of your pulmonary or gastrointestinal system. For example, endoscopy is a procedure in which your doctor inserts a camera down into your esophagus (food pipe) to see the inner lining of the esophagus and stomach.

A colonoscopy is a diagnostic test in which a camera is inserted into the rectum to visualize the intestines. And a bronchoscopy is a procedure in which a camera is inserted into the windpipe to visualize parts of your respiratory system.

Tumors can often be identified with these tests, and during one of these interventional examinations, a biopsy can be obtained as well.


If you have a tumor, you may need to have a biopsy so that your medical team can plan your treatment. A small sample of abnormal-appearing tissue can be safely removed so that it can be examined with a microscopic evaluation. This is often done as part of a bronchoscopy or an endoscopy.

A pathology report describes the type of tumor, the tumor grade, and the tumor stage.

  • Tumor grade describes the aggressiveness of the tumor and how likely it is to spread.
  • Tumor stage describes whether the tumor has spread, and how extensively it has metastasized in the body. Tumor staging is dependent on the pathology as well as the imaging tests. 

Results of the diagnostic tests are used to plan the treatment of carcinoid syndrome and the carcinoid tumor.


There are three major objectives when it comes to treatment of carcinoid syndrome. Your symptoms, such as diarrhea, rapid heart, and restlessness have to be managed. Medications that interfere with tumor-produced hormone activity are often useful. And treatment of the tumor is often necessary.

Symptom Management

Depending on your symptoms, you may need medical treatment to control the effects of a carcinoid tumor. Medications can be used to slow a rapid heart rate, to aid heart function in heart failure, to lower a high temperature, and to help you breathe more easily.

If you have carcinoid syndrome, you will only need symptomatic treatment for the effects that you experience. Your treatment needs can change over time as your hormone levels—and the effects of the condition—fluctuate.

Carcinoid crisis: The effects of carcinoid syndrome can be quite severe. While it is not common, some people need to have assistance with breathing or heart function. Carcinoid crisis is not necessarily associated with larger tumors or metastatic tumors, and it can occur with carcinoid tumors that are relatively small in size.

Hormone Treatment

If you have carcinoid syndrome, you may be treated with somatostatin analogues, which are medications that interact with hormones in the body to diminish the effects of carcinoid syndrome.

  • Sandostatin (octreotide), Somatuline (lanreotide), and Signifor (pasireotide) are somatostatin analogues used in carcinoid syndrome. 
  • Xermelo (telotristat ethyl) and Afinitor (everolimus) are also hormone-modulating medications used to treat carcinoid syndrome and other tumors. 

In general, these treatments do not shrink the tumor or stop it from growing, but they can alleviate the impact of hormone overproduction.

Cancer Treatment

Carcinoid tumors often require several treatment strategies. Surgical removal of the tumor is often necessary. Radiation treatment can shrink the size of the tumor and any metastases before and/or after surgery. Some tumors, particularly those that cannot be completely removed surgically, require chemotherapy, immunotherapy, or targeted therapies. 

The prognosis of carcinoid tumors is good, with over a 90 percent 5-year survival for tumors diagnosed at an early stage.

 A Word From Verywell

Carcinoid syndrome is relatively uncommon. Sometimes, it can be completely cured, but even when the condition is not curable, it can typically be managed and has a good prognosis. 

If you or a loved one is diagnosed with carcinoid syndrome, it is important that you familiarize yourself with the common symptoms so that you will know if it acts up or if a tumor recurs.

Often, people who have rare medical conditions can benefit from joining support groups. Because carcinoid syndrome is not common, you might not have a support group in your area. Consider finding a community online. Your medical team can provide you with information about reputable groups and associations.

If your tumor is not completely cured, you may be interested in participating in a research study, and your medical team or a support group may be able to direct you to resources.

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