We were on summer vacation on the shores of Lake Michigan in the summer of ’98. One night I started having incredible pain in my gut. I was literally writhing on the floor in pain. My wife went to the store and brought back all the stomach relief medicine she could find. It didn’t help. Gradually the pain subsided. What we didn’t know at the time was that I had a Carcinoid tumor in my intestine.
Usually NOT. It may infrequently produce antibodies that make it less effective, but this is in only a very small minority of cases. In some other cases it becomes less effective AT THE SAME DOSAGE because the tumors are growing. In most cases it is better to take it early in the disease, especially if carcinoid syndrome is present and blood serotonin levels are elevated because it will prevent carcinoid heart disease and inhibit tumor growth as well as prevent carcinoid syndrome symptoms.
If I understand your question correctly, you state that a diagnosis of carcinoid syndrome is suspected because of symptoms and high urine 5-HIAA, but the CT scan is normal and you want to know what other tests should now be done to prove the diagnosis. Failure to find carcinoid tumors when proven carcinoid syndrome is present is not so rare. This occurs initially in 10% of cases.
Carcinoid syndrome requires one or more of the following for laboratory confirmation of the diagnosis: increased blood serotonin with decreased blood tryptophan, increased chromogranin A and increased urine 5HIAA or indole-3-acetic acid. In spite of the symptoms, if these criteria are not present, carcinoid syndrome is not the diagnosis.
It can be carcinoid syndrome. How high is the 5-HIAA and was the urine collected on a serotonin-free diet? If it was more than just slightly elevated, then confirm its significance by testing blood serotonin, which should be increased; blood tryptophan, which should be decreased; and chromogranin, A which should be increased. If one or two of these are clearly abnormal, you should check the liver for metastatic tumor - by CT scan with contrast or MRI. If negative, do an OctreoScan to search for tumor foci not seen by the other imaging techniques.
Carcinoid cancer and related neuroendocrine tumors (NETs) are small, slow growing tumors found mostly in the gastrointestinal system, but can be in other parts of the body such as the pancreas and the lung. Since most of these grow very slowly, compared to other cancers, it usually takes many years before they become sizable or cause symptoms.