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

Carcinoid syndrome is the pattern of symptoms seen in 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 make niacin and certain proteins, but in carcinoid syndrome, it forms serotonin instead. Most serotonin is changed 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.

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

5-HIAA levels in urine are higher than normal 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, fluorouracil, iodine solutions, phenacetin, MAO inhibitors (certain anti-depressant drugs), isoniazid, and phenothiazine drugs (Compazine, Thorazine).

Blood tests may show higher than normal levels of serotonin levels and chromogranin A, and lower than normal levels of tryptophan.

The OctreoScan is a scanning test used to identify most carcinoids and other neuroendocrine tumors. A CT and MRI scan may be done along with the OctreoScan to see how well treatment of the carcinoid tumor is working.

Less frequent blood tests may check levels of histamine, bradykinin, neurone-specific enolase, calcitonin, Substance-P, neurokinin-A, and pancreatic polypeptide.

An examination may show heart valve lesions or signs of niacin-deficiency disease (pellagra).