Carcinoid Syndrome

Carcinoid syndrome is a rare condition that occurs when certain tumors release large amounts of hormones and other chemicals into your bloodstream, causing a range of uncomfortable and sometimes serious symptoms that can significantly affect your daily life.

Table of contents

• What is carcinoid syndrome?
• What causes this condition?
• Signs and symptoms
• Possible complications
• How is it diagnosed?
• Treatment options
• Living with carcinoid syndrome

What is carcinoid syndrome?

Carcinoid syndrome happens when rare cancerous tumors called carcinoid tumors, which are a type of neuroendocrine tumor (NET), release certain chemicals into your bloodstream. These tumors start in specialized cells in your neuroendocrine system, which is the part of your body that makes and releases hormones.^[1][2]

This syndrome is not common. Studies suggest that only about 1 in 5 people with neuroendocrine tumors develop carcinoid syndrome. Since NETs themselves affect only about 5 in 100,000 people in the United States, carcinoid syndrome is quite rare.^[2]

The syndrome typically occurs in people who have carcinoid tumors that are advanced. Most often, carcinoid syndrome develops when tumors in your digestive system or lungs have spread to your liver. Sometimes, a carcinoid syndrome diagnosis is the first sign that you have a neuroendocrine tumor.^[1][2]

• Gastrointestinal tract
• Lungs
• Liver
• Heart

What causes this condition?

Carcinoid syndrome is caused by neuroendocrine tumors that have spread to the liver. The majority of these tumors come from the midgut, which includes the small intestine, appendix, and the first part of the large bowel. When NETs are only in their original location and have not spread, they typically do not cause carcinoid syndrome because the liver breaks down the hormones and other substances they produce. However, once the cancer spreads to the liver or other areas, these chemicals can flood your system.^[3][9]

The tumors release unusually large amounts of serotonin and other substances called biogenic amines. Serotonin is a chemical that normally helps regulate various body functions. When too much is released into your bloodstream, it causes the various symptoms of carcinoid syndrome.^[2][3]

Less commonly, tumors from the foregut (stomach, first part of small intestine) or lungs can also cause carcinoid syndrome.^[3]

Signs and symptoms

The signs and symptoms of carcinoid syndrome depend on which chemicals the tumor releases into your bloodstream. The most common symptoms include:^[1][2]

• Skin flushing: The skin on your face and upper chest feels hot and changes color, ranging from pink to purple. These flushing episodes may last from a few minutes to a few hours or longer. Flushing may happen for no obvious reason, though it can be triggered by stress, exercise, or drinking alcohol.^[1]
• Diarrhea: Frequent, watery stools sometimes accompanied by abdominal cramping. This can be severe, with some people experiencing more than 30 episodes a day. About 80 out of every 100 people with carcinoid syndrome have diarrhea.^[1][6]
• Wheezing and shortness of breath: Asthma-like symptoms may occur at the same time as skin flushing.^[1][2]
• Rapid heartbeat: Periods of a fast heart rate or feeling like your heart is racing.^[1][2]

Other symptoms that may occur include:^[2][6]

• Purplish areas of spiderlike veins on your nose and upper lip
• Fatty stools that smell bad
• Swelling of your feet and legs
• Loss of interest in sex or erectile dysfunction
• Yellowing of your skin and the whites of your eyes (jaundice)
• Dizziness or feeling faint
• Abdominal pain

About 85 out of every 100 people with carcinoid syndrome experience flushing of the skin.^[6]

Possible complications

Carcinoid syndrome can cause several serious complications that require careful monitoring and management.^[2]

Carcinoid heart disease

This is a rare but potentially life-threatening complication that happens when tumors release hormones that affect the linings in your heart chambers, valves, and blood vessels. Over time, a buildup of plaque or scar tissue can make the valves thicker, affecting how the heart works. This condition occurs in up to 50 out of every 100 people with carcinoid syndrome. Symptoms are usually vague and may not appear until the condition is severe. They include feeling breathless, tiredness, swelling in your body, and weight loss. Carcinoid heart disease may lead to heart failure.^[2][6]

Carcinoid crisis

Carcinoid crisis is an extremely rare but life-threatening condition that can happen when your carcinoid syndrome goes undiagnosed or untreated. It occurs when NETs release very large amounts of hormones and proteins. Triggers include surgery, other medical procedures, or traumatic events like an injury from an accident.^[2][8]

Symptoms of carcinoid crisis include:^[2][6]

• Wide changes in blood pressure, including very low blood pressure
• Sudden, severe flushing
• Severe shortness of breath
• Confusion
• Very severe diarrhea

Carcinoid crisis is a medical emergency. People with carcinoid syndrome or a neuroendocrine tumor should carry a card listing their medical condition in case they need emergency medical care.^[2]

Other complications

Additional complications may include:^[2]

• Mesenteric fibrosis: Inflammation and scarring of the tissue that attaches your intestines to the wall of your belly
• Depression: Carcinoid syndrome may affect your body’s ability to process tryptophan, an essential amino acid that helps make serotonin. Serotonin is a brain chemical that manages mood, behavior, and sleep.

How is it diagnosed?

Your doctor will first assess your signs and symptoms to rule out other causes of skin flushing and diarrhea. If no other causes are found, your doctor may suspect carcinoid syndrome and recommend further tests.^[7]

Urine tests

Your body breaks down the hormone serotonin into a substance called 5-HIAA (5-hydroxyindoleacetic acid). Your doctor can test for this in your urine. An excess amount of this substance indicates that your body is processing extra serotonin, which is commonly released by carcinoid tumors. This is the primary diagnostic test for carcinoid syndrome.^[3][6][7]

Blood tests

Your blood may contain high levels of certain substances that are released by carcinoid tumors. Blood tests can check for substances such as chromogranin A and NT-proBNP (a protein that helps doctors assess how well your heart is working). Blood tests may also measure different mineral and vitamin levels.^[6][7]

Imaging tests

Imaging tests help locate the primary carcinoid tumor and determine whether it has spread. Your doctor may start with a CT scan of your abdomen, because most carcinoid tumors are found in the gastrointestinal tract. Other scans, such as MRI or nuclear medicine scans, may be helpful in certain situations.^[7]

Examination with a scope or camera

Your doctor may use a long, thin tube equipped with a lens or camera to examine areas inside your body. An endoscopy, which involves passing a scope down your throat, may help your doctor see inside your gastrointestinal tract. A bronchoscopy, which uses a scope passed down your throat and into your lungs, can help find lung carcinoid tumors. Passing a scope through your rectum (colonoscopy) can help diagnose rectal carcinoid tumors.^[7]

Biopsy

A sample of tissue from the tumor may be collected to confirm your diagnosis. What type of biopsy you undergo depends on where your tumor is located.^[7]

Treatment options

Treating carcinoid syndrome involves treating the cancer itself and using medications to control your specific signs and symptoms. Complete surgical removal of all tumor tissue, when possible, is the best treatment because it may result in a complete and permanent cure.^[1][11]

Surgery

When surgery is feasible, removing the tumor can be the most effective treatment. Surgical options may be used to reduce tumor burden even when complete removal is not possible.^[3][7]

Medications to control symptoms

Somatostatin analogs are the main medications used to control carcinoid syndrome symptoms. These include octreotide and lanreotide. These synthetic versions of a natural hormone have a longer half-life than the natural hormone and work by controlling hormone secretion from the tumors. Studies show they are useful in approximately 40% of patients and can control both symptoms and tumor growth.^[3][11]

Other medications that may be used include:^[11]

• Standard antidiarrheal medications for controlling diarrhea
• Serotonin antagonists if needed for severe diarrhea and malabsorption
• Histamine blockers for symptoms related to increased histamine production, such as swelling
• Clonidine for severe flushing
• Corticosteroids for severe and prolonged carcinoid crises

Other treatments

Additional treatment options include:^[3]

• Peptide receptor radioligand therapy (PRRT): A type of targeted radiation therapy
• Liver-directed interventions to reduce tumor burden when tumors have spread to the liver
• Intravenous fluid infusion for patients with severe diarrhea who develop dehydration

Living with carcinoid syndrome

While medical treatment is important, you can also make lifestyle changes to help manage symptoms and improve your quality of life.^[13]

Dietary changes

Certain foods and beverages can trigger or worsen flushing and other symptoms. You should avoid:^[13][17]

• Alcoholic and caffeinated drinks
• Foods high in amines, such as aged cheese, smoked fish, and smoked meats
• Foods high in serotonin, such as nuts, bananas, and raw tomatoes
• Wheat bran and prunes if you have diarrhea

Helpful dietary practices include:^[13]

• Eating four to six smaller but nutritious meals daily instead of three large meals
• Drinking fluids frequently throughout the day in small amounts if you have diarrhea
• Maintaining a healthy and balanced diet

You may need to supplement your diet with essential nutrients and vitamins. Supplemental niacin is especially important, as the tumors can deplete stores of tryptophan that would otherwise be used to generate niacin. If you’re unsure how to adjust your diet, speak to your doctors about seeing a nutritionist or dietitian.^[11][13]

Activity and stress management

Strenuous activity and high stress levels can trigger symptoms. Consider lowering the intensity of your exercise and engaging in light physical activity such as short walks and jogs. If you need help with physically demanding tasks, seek assistance from family and friends.^[13]

Try breathing exercises or other relaxation techniques to manage stress. These practices can potentially relieve stress and fatigue and improve your coping and well-being.^[13]

Emotional support

Living with carcinoid syndrome can be emotionally challenging. You may experience a range of feelings including shock, fear, anger, sadness, or feeling numb. These are all normal reactions.^[14]

Talking to your friends and relatives about your condition can help, though some people may find this difficult. You might find it easier to talk to someone other than your own family and friends, such as a counselor or members of a support group.^[14]

Support groups provide a safe space to meet other people with similar experiences. They can be useful in helping you feel more understood and less alone, and they offer a place to discuss practical information about managing your condition.^[13]

Important precaution

Because carcinoid crisis can be triggered by surgery or medical procedures, people with carcinoid syndrome or a neuroendocrine tumor should carry a card listing their medical condition in case they need emergency medical care.^[2]