Carcinoid Syndrome

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What is carcinoid syndrome?

Carcinoid syndrome is a cluster of symptoms that occurs in some people with carcinoid tumors. Carcinoid tumors are a rare form of cancer that arises in neuroendocrine cells. These cells have both nerve cell and hormone-producing cell traits. They are present throughout the body to help regulate various functions. They are most numerous in the digestive system and this is where most carcinoid tumors develop. Carcinoid tumors can also affect the lungs, but rarely develop in other organs.

Carcinoid syndrome happens when carcinoid tumors begin making and releasing large amounts of hormones, such as serotonin. This causes a variety of symptoms, such as carcinoid syndrome rash, skin flushing, diarrhea, and difficulty breathing.

The syndrome doesn’t affect everyone with carcinoid tumors. In most cases, it occurs in people with advanced tumors of the liver or lung. About 10% of people with this type of cancer will end up with a carcinoid syndrome diagnosis. However, the incidence may be as high as 40% of people with carcinoid tumors. The syndrome can be difficult to diagnose and isn’t always recognized for what it is. It’s easy to mistake it for other conditions and even medication side effects. Your doctor can confirm the diagnosis with carcinoid syndrome tests, including urine and blood tests.

Treating carcinoid syndrome generally involves treating the underlying cancer. Because the tumors causing carcinoid syndrome are usually advanced, this can be difficult. The main treatment is surgery to remove all or part of the tumor. If this is not possible, medicines may help control tumor growth and relieve symptoms.

If carcinoid syndrome progresses, it can cause heart valve disease and heart failure. It can also lead to bowel obstruction, gastrointestinal bleeding, and carcinoid crisis, which is potentially fatal.

What are the symptoms of carcinoid syndrome?

The symptoms of carcinoid syndrome depend on the hormone the tumor is releasing. One of the most common and serious ones is serotonin. High levels of serotonin can affect digestion, blood pressure, heart rate, muscle control, and mental status.

Common symptoms of carcinoid syndrome

The most common symptoms of carcinoid syndrome include:

  • Breathing problems and other asthma-like symptoms, such as wheezing and shortness of breath
  • Rapid heart rate
  • Telangiectasias, which is widened blood vessels on the skin that look like purplish spider veins, especially on the nose and upper lip
  • Uncomfortable skin flushing, especially of the face, neck, and upper chest, which can last for minutes or hours and range from pink to a dark purple

Certain things can trigger symptoms, particularly skin flushing. This includes emotional stress, physical exertion, and eating or drinking something hot or specific foods or drinks, such as alcohol, chocolate, or blue cheese.

Serious symptoms that might indicate a life-threatening condition

In some cases, carcinoid syndrome can become serious and even life threatening. Seek immediate medical care (call 911) if you, or someone you are with, have any of the following:

Carcinoid tumors are slow-growing and rarely cause symptoms or problems in the early stages. If a tumor is causing carcinoid syndrome, it is probably in advanced stages, but may or may not be diagnosed. Because there are more common causes of many of carcinoid syndrome symptoms, a diagnosis is oftentimes delayed. Doctors will likely explore other common causes first. Once other causes are ruled out, doctors can use urine tests, blood tests, and imaging exams to make a carcinoid syndrome diagnosis.

What causes carcinoid syndrome?

Carcinoid syndrome occurs when carcinoid tumors secrete high levels of hormones, such as serotonin. Carcinoid tumors can occur anywhere, but are most common in the digestive system and lungs. Not all carcinoid tumors will cause carcinoid syndrome. Only a small percent secrete high levels of hormones. And when they do, their location can play a role in whether or not carcinoid syndrome develops.

If tumors in the intestines secrete hormones into blood, the blood must go to the liver first before it circulates to the rest of the body. A healthy liver can neutralize these substances before they can cause symptoms. However, tumors in the lungs that secrete hormones do so into blood that does not go directly to the liver. This blood can circulate out to the body and cause problems. And when tumors affect the liver itself, they can secrete hormones directly into the blood and out to the body without being neutralized. Most cases of carcinoid syndrome are due to advanced carcinoid tumors that have spread to the liver.

What are the risk factors for carcinoid syndrome?

About 10% of people with a carcinoid tumor will get carcinoid syndrome. The risk factors for carcinoid tumor include:

  • African American race
  • Age 50 years or older
  • Genetic syndromes, including multiple endocrine neoplasia type 1 and neurofibromatosis type 1
  • Other stomach conditions that damage the stomach or reduce stomach acid production

Reducing your risk of carcinoid syndrome

Treating carcinoid tumors before they become advanced offers the best chance of reducing your risk of carcinoid syndrome. Unfortunately, carcinoid tumors rarely cause symptoms in the early stages. As a result, carcinoid tumors are often advanced at diagnosis.

How is carcinoid syndrome treated?

Treating the carcinoid tumor is the main way to treat carcinoid syndrome. This usually involves surgery. If surgery can remove the entire tumor, it will cure carcinoid syndrome. However, this is not always possible since carcinoid tumors are typically advanced when they cause carcinoid syndrome.

When surgery can’t remove the whole tumor, it may still be useful to remove part of the tumor. This “debulking” of the tumor can relieve symptoms of carcinoid syndrome. Other options for relieving symptoms include:

  • Biologic therapy to shrink the tumor
  • Chemotherapy to shrink the tumor, although this option has limited use in carcinoid tumors as only one-third of patients have a beneficial response
  • Somatostatin analogs, such as octreotide (Sandostatin) and lanreotide (Somatuline Depot), which is the mainstay of symptomatic treatment. These drugs work by blocking the release of hormones from the tumor. Octreotide may slow the growth of the tumor as well.
  • Telotriastat (Xermelo) to relieve diarrhea in combination with somatostatin analogs

When the tumor is in the liver, removing the affected part of the liver may be an option. Other options for treating liver tumors include:

  • Ablation with radiofrequency (heat) or cryotherapy (cold) to destroy tumor cells
  • Hepatic artery embolization, which is a catheter-based procedure. It clots off arteries in the liver that supply blood to the tumor.
  • Infusion of chemotherapy drugs directly into the liver to kill cancer cells

People with carcinoid syndrome should also make dietary adjustments to avoid triggering symptoms. This includes avoiding alcohol, large meals, hot foods and beverages, and high-tyramine foods and beverages, such as aged cheeses. Tyramine is an amino acid—a building block of proteins. Pickled and fermented foods, home-brewed beer, dried fruit, and citrus fruits are dietary sources of tyramine.

What are the potential complications of carcinoid syndrome?

Potential complications of carcinoid syndrome include:

  • Bowel obstruction from the tumor or from cancer that has spread to nearby lymph nodes that enlarge and narrow the intestine. Surgery may be necessary.
  • Heart valve disease due to thickening of the valves. This can eventually lead to heart failure. Surgical heart valve repair may prevent this and medications can help manage it.
  • Carcinoid crisis that may be fatal. This severe reaction often involves severe flushing, low blood pressure, confusion, and difficulty breathing. Triggers include anesthesia and chemotherapy. Medications can help reduce the risk of carcinoid crisis.

The carcinoid syndrome prognosis can be different from a carcinoid tumor without the syndrome. It depends on the location of the tumor. When the tumor has spread to the liver, the outlook is generally poorer than other locations.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2020 Jul 14
  1. Carcinoid Syndrome. Mayo Foundation for Medical Education and Research. https://www.mayoclinic.org/diseases-conditions/carcinoid-syndrome/symptoms-causes/syc-20370666
  2. Carcinoid Syndrome. Merck Manual Professional Version. https://www.merckmanuals.com/professional/endocrine-and-metabolic-disorders/carcinoid-tumors/carcinoid-syndrome
  3. Carcinoid Syndrome. National Organization for Rare Disorders. https://rarediseases.org/rare-diseases/carcinoid-syndrome/
  4. Carcinoid Syndrome. U.S. National Library of Medicine. https://medlineplus.gov/ency/article/000347.htm
  5. Carcinoid Syndrome 101. Carcinoid Cancer Foundation. https://www.carcinoidsyndrome.org/understanding-carcinoid-syndrome/carcinoid-syndrome-101/
  6. Neuroendocrine Tumor of the Gastrointestinal Tract. American Society of Clinical Oncology. https://www.cancer.net/cancer-types/neuroendocrine-tumor-gastrointestinal-tract/introduction
  7. Review of Carcinoid Cancer. Carcinoid Cancer Foundation. https://www.carcinoid.org/for-patients/general-information/a-review-of-carcinoid-cancer/
  8. What Is Serotonin? Endocrine Society. https://www.hormone.org/your-health-and-hormones/glands-and-hormones-a-to-z/hormones/serotonin
  9. MAOIs and Tyramine: Foods in Your Diet May Lead to Dangerous Side Effects. Psycom. https://www.psycom.net/maoi-diet-tyramine/

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