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What Is Carcinoid Syndrome?

By Ellen Greenlaw
WebMD Feature

Carcinoid syndrome is a set of symptoms caused by some carcinoid tumors, which grow out of cells that are part of the endocrine system. These tumors sometimes produce too many hormones, such as serotonin, which cause the symptoms of carcinoid syndrome.

Carcinoid tumors are usually slow to grow and spread. When found early, carcinoid tumors can often be successfully treated or cured. But by the time the symptoms of carcinoid syndrome appear, the tumor has usually spread. This makes it important to diagnose the tumors and carcinoid syndrome as early as possible.

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"The most important step in diagnosing carcinoid syndrome is thinking of it," says Richard Warner, MD, professor of medicine at the Mount Sinai School of Medicine and medical director of the Carcinoid Cancer Foundation. "Unfortunately, the delay in diagnosis is often as long as 5 to 7 years from the time the first symptom of carcinoid syndrome appears." So it's important for people with on-going health problems to be aware of these symptoms.

What are the symptoms of carcinoid syndrome?

The most common symptoms of carcinoid syndrome include:

  • Diarrhea
  • Flushing of the skin or face
  • Heart palpitations
  • Stomach cramps
  • Shortness of breath 
  • Wheezing

"The facial flushing of carcinoid syndrome is usually a dry flushing, and not associated with sweating like other kinds of flushing," says James Yao, MD, associate professor and deputy chair of the Department of Oncology at the University of Texas MD Anderson Cancer Center in Houston. "The flushing is often a symptom that others notice before patients do. They may not feel it themselves."

These symptoms may be made worse by stress, physical exertion, or drinking alcohol. Eating certain foods, such as aged cheese like cheddar or stilton cheese, salted or pickled meats, or other foods that contain tyramine may also trigger symptoms. 

"Stress and alcohol are definite triggers for the flushing," says Yao. "And stress and certain foods can trigger the diarrhea." These triggers can often be important clues in diagnosing carcinoid syndrome.

How common is carcinoid syndrome?

Carcinoid syndrome only occurs in about 10% of people who have carcinoid tumors. Although many carcinoid tumors produce hormones, these hormones often don't make it into the body's general bloodstream. This is because blood from the digestive tract usually flows through the liver before going out to the rest of the body. So the liver is able to dissolve any excess hormones before they can reach other parts of the body. But when the tumors have spread to the liver or other parts of the body the excess hormones can cause the symptoms of carcinoid syndrome.

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