Definition
Carcinoid syndrome is a group of symptoms associated with carcinoid tumor (see bronchial adenoma).

Causes, incidence, and risk factors

Carcinoid syndrome is the pattern of symptoms exhibited by people with carcinoid tumors. These tumors may occur in the small intestine, colon, bronchial tubes, or appendix.

Carcinoid tumors secrete excessive amounts of the hormone serotonin as well as other chemicals that cause the blood vessels to dilate (open). These tumors may also cause diarrhea and wheezing (asthma).

There are wide variations in the chemicals secreted by these tumors, and the symptoms depend on the mix of chemicals made by the particular tumor.

Normally, an amino acid called tryptophan is used by the body to manufacture niacin and certain proteins, but in carcinoid syndrome, it gets diverted to form serotonin. Most serotonin is converted by the body to 5-hydroxy indole acetic acid (5-HIAA).

The most bothersome symptoms include bright red facial flushing, diarrhea (which may be explosive and severe) and occasionally wheezing. A specific type of heart valve damage may occur, as well as other cardiac problems.

In children, carcinoid tumors usually occur in the appendix, and removal of the appendix usually results in a complete cure.

Symptoms

 
• Abdominal pain, intermittent  
• Flushing  
• Diarrhea  
• Wheezing  
• Heart palpitations  
• Low blood pressure

Signs and tests

 
• 5-HIAA levels in urine are elevated in 75% of cases. Certain foods and medicines must be avoided for a couple of days before this test, and on the day the urine is collected. These include bananas, pineapple and its juice, red plums, avocado, walnuts, kiwi fruit, tomatoes, various cough medicines, muscle-relaxing medicines, acetaminophen (Tylenol), caffeine, fluorouacil, iodine solutions, phenacetin, MAO inhibitors (certain anti-depressant drugs), isoniazid, and phenothiazine drugs (Compazine, Thorazine).  
• Serotonin levels in blood may be elevated.  
• Chromogranin A in blood may be elevated.  
• Tryptophan in blood may be decreased.  
• The OctreoScan - a radio-isotope scanning test - has been approved by the U.S. Food and Drug Administration. This test will identify most carcinoids and any other neuroendocrine tumors.  
• A CT and MRI scan may be done along with the OctreoScan to monitor the progress of treatment of the carcinoid tumor.  
• Less frequent tests may include histamine, bradykinin, neurone-specific enolase, calcitonin, Substance-P, neurokinin-A, and pancreatic polypeptide.

An examination may indicate heart valve lesions or signs of niacin-deficiency disease (pellagra). Signs of pellagra develop when most of the available tryptophan is used by the tumor to produce serotonin, which then prevents the body from manufacturing niacin.

Treatment

Surgery with complete removal of the tumor tissue is usually the first line treatment. It can result in permanent cure if it is possible to remove the tumor entirely.

Even when the entire tumor cannot be removed, removing large portions of the tumor (debulking) can effectively relieve the symptoms by decreasing the amount of harmful hormones being produced and flooding the circulation.

There are also some new procedures for treating tumors that have spread or metastasized to the liver.

The mainstay of treatment for advanced carcinoid tumors that cannot be removed surgically is Sandostatin (octreotide) injections. In many cases, this anti-hormone drug inhibits and reverses the growth of the tumors.

Sandostatin is given by injection 2-3 times a day at first. After a 2- to 4-week period, the injection may be changed to once a month using a long-acting release (LAR) dosage. This often improves symptoms of the carcinoid syndrome, and decreases tumor progression.

Interferon is another drug often given with octreotide. It is referred to as an immuno-modulator. Its effect is to suppress or stop the growth of the tumor.

One of several combinations of chemotherapy may be given by intravenous injection or by mouth for carcinoid syndrome. If one combination is does not work, another combination may be effective, and overall about one-third of patients benefit from chemotherapy.

Increased protein and a low-fat diet are often recommended. Multivitamin mineral and low-dose Nicotinic Acid (niacin) supplements may be prescribed. Other items sometimes recommended are fish oil capsules, electrolyte supplements, and in some cases, large portions of nutmeg. Patients are advised to ingestion of alcohol, large meals, and foods high in tyramine, as these may provoke symptoms.

A serotonin antagonist may be prescribed to control diarrhea and inadequate absorption of nutrients from the intestines (malabsorption).

Sandostatin and similar medications may be effective in reducing the episodes of flushing and diarrhea, and in reversing the blood pressure changes. There are other medications that may be prescribed for symptoms as well.

Some common medicines, like selective serotonin reuptake inhibitors (SSRIs, such as Paxil, Serzone, and Prozac) may make symptoms worse by increasing levels of serotonin. However, these medicines should be discontinued ONLY on the advice of a doctor, since stopping them abruptly may cause withdrawal symptoms, and because the depression they treat may cause health problems as well.

Support Groups
Learn more about carcinoid syndrome and get support from The Carcinoid Cancer Foundation.

Expectations (prognosis)
The course of the illness in patients with carcinoid syndrome is different than those patients who have carcinoid tumors without the syndrome. The outlook is more favorable with the addition of new treatment methods, such as Sandostatin and others. The survival rate is variable.

Complications

 
• Hypotension increases the risk of falls and subsequent injury.  
• Gastrointestinal bleeding.  
• Bowel obstruction from tumor mass.  
• Right-sided heart failure.

Calling your health care provider
Call for an appointment with your health care provider if symptoms occur that are suggestive of carcinoid syndrome.

Prevention
Treatment of the associated tumor reduces the risk of carcinoid syndrome.

Medical Encyclopedia

All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.