Carcinoid syndrome affects certain people who have neuroendocrine tumors (NETs). Carcinoid syndrome can occur when an NET secretes hormones into the bloodstream. This can cause symptoms such as facial flushing and diarrhea.

NETs develop in neuroendocrine cells, which produce hormones in response to signals from the nervous system. Neuroendocrine cells are found in various organs of the body, such as the lungs and pancreas.

Hormones are chemical messengers carried in the blood to tissues and organs. If the NET secretes high enough levels of hormones into the bloodstream, it can cause a range of symptoms.

Read on to learn more about the symptoms and causes of carcinoid syndrome. This article also looks at how doctors diagnose the condition, treatment options, and more.

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Carcinoid syndrome can cause a variety of symptoms, such as:

Flushing is the most common symptom of carcinoid syndrome. It affects around 85% of people with the condition. Flushing typically lasts anywhere from 30 seconds to 30 minutes, though it may last longer.

Other common symptoms include diarrhea and cardiac issues. About 80% of people with the condition have diarrhea, and 60–70% of people have cardiac issues.

The American Cancer Society notes that around 10% of NETs cause carcinoid syndrome. Medical professionals previously referred to NETs as carcinoid tumors.

Carcinoid syndrome occurs when NETs release a high enough level of hormones to cause symptoms.

The liver usually inactivates hormones that the body does not use. However, carcinoid syndrome can occur if the hormones directly enter the systemic circulation or if something affects the liver’s function.

Carcinoid syndrome is most likely to occur as a result of NETs that develop in the midgut. The midgut includes the appendix, small intestine, cecum, and ascending colon.

Additionally, certain NETs, such as those that develop in the ovaries and lungs, may release hormones directly into the bloodstream without spreading to the liver.

Learn about what can cause tumors.

A doctor may use certain laboratory tests to check for signs of carcinoid syndrome. The doctor may also use imaging tests to check the tumor’s location.

The first test a doctor may use measures the amount of 5-hydroxyendolacetic acid (5-HIAA) in a person’s urine over 24 hours.

5-HIAA is a product of serotonin breakdown. Serotonin is a hormone that NETs can secrete. If a person has a high level of 5-HIAA in their urine, it may indicate that they have carcinoid syndrome.

Before a 5-HIAA test, a doctor will give a person a list of foods and medications they should avoid for at least 1 day before the test. Consuming certain foods or medications can affect the results of the test.

A doctor may also check a person’s chromogranin A (CgA) level. NETs also secrete this molecule.

A doctor may then use the following imaging tests to diagnose carcinoid syndrome:

A doctor can provide more information about the tests they order and answer any questions a person may have.

Treatment for carcinoid syndrome is different for each person.

Medical treatments

A doctor may treat carcinoid syndrome using:

  • surgery to remove all or most of the NET
  • medications that inhibit the release of certain hormones, such as somatostatin analogs
  • antidiarrheal medication
  • chemotherapy
  • radiotherapy
  • targeted therapy

Managing symptoms

Some people with carcinoid syndrome find that the following trigger their symptoms:

A person may find that their symptoms reduce if they avoid alcohol and manage stress. A person may help reduce their stress levels by:

  • reaching out to family and friends
  • getting enough quality sleep
  • avoiding smoking
  • meditating

It is best to contact a doctor for advice about how much exercise a person should aim for each week. The doctor can also advise on more ways to manage symptoms of carcinoid syndrome.

Learn more about managing stress.

It is best for a person to contact a doctor if they notice any signs and symptoms of carcinoid syndrome. Over time, carcinoid syndrome can damage parts of the heart.

Receiving an accurate diagnosis and beginning treatment as early as possible may help reduce a person’s chances of developing heart issues.

Carcinoid syndrome can damage the heart valves. This can lead to heart failure or valvular heart disease.

Additionally, carcinoid syndrome can cause a potentially life threatening condition called carcinoid crisis. Carcinoid crisis occurs when NETs produce a large amount of hormones. This can cause a person to experience:

  • low blood pressure
  • difficulty breathing
  • sustained facial flushing

Carcinoid crisis can be a result of triggers such as:

Seeking medical advice as early as possible can help a person begin the right treatment and reduce the risk of complications.

Here are some frequently asked questions about carcinoid syndrome.

Does carcinoid syndrome mean cancer?

Carcinoid syndrome may indicate that a person has an NET. In some cases, the tumor may be cancerous.

A person can speak with a doctor about what their diagnosis means.

What are the triggers of carcinoid syndrome?

Triggers of carcinoid syndrome include:

  • stress
  • alcohol
  • heavy exercise

Avoiding these triggers can help a person manage their symptoms.

How do you detect carcinoid syndrome?

A doctor can detect carcinoid syndrome using:

  • 24-hour 5-HIAA tests
  • CgA level tests
  • imaging tests, such as CT scans or MRIs

Carcinoid syndrome is a condition that can occur if a person has a tumor called a NET. Carcinoid syndrome develops as a result of the NET releasing high levels of hormones.

Certain factors, such as stress or alcohol intake, may trigger symptoms such as facial flushing.

A doctor can treat carcinoid syndrome with surgery. They may also recommend medication. Without treatment, carcinoid syndrome may cause heart issues and other complications.

It is best to contact a doctor as soon as there are concerns about carcinoid syndrome. The doctor can order tests to determine the cause of the symptoms and advise on a suitable treatment plan.