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Carcinoid syndrome is a paraneoplastic syndrome comprising the signs and symptoms that occur secondary to neuroendocrine tumors (formerly known as carcinoid tumors). [1] The syndrome is caused by neuroendocrine tumors most often found in the gut releasing biologically active substances into the blood causing symptoms such as flushing and diarrhea, and less frequently, heart failure, vomiting ...
5-HIAA is the major urinary metabolite of serotonin, a ubiquitous bioactive amine. Serotonin, and consequently 5-HIAA, are produced in excess by most carcinoid tumors, especially those producing the carcinoid syndrome of flushing, hepatomegaly (enlarged liver), diarrhea, bronchospasm, and heart disease. Quantitation of urinary 5-HIAA is the ...
About 10% of carcinoids secrete excessive levels of a range of hormones, most notably serotonin (5-hydroxytryptamine), causing: Flushing (serotonin itself does not cause flushing). Potential causes of flushing in carcinoid syndrome include bradykinins, prostaglandins, tachykinins, substance P, and/or histamine, diarrhea, and heart problems.
Enterochromaffin cells, which give rise to carcinoid tumors, were identified in 1897 by Nikolai Kulchitsky and their secretion of serotonin was established in 1953 [105] when the "flushing" effect of serotonin had become clinically recognized. Carcinoid heart disease was identified in 1952, and carcinoid fibrosis in 1961. [105]
Pentagastrin is also used as a stimulation test to elevate of several hormones, such as serotonin. It provokes flushing and is useful in evaluating patients who describe flushing, but have normal or only marginally elevated biochemical markers for carcinoid syndrome. [citation needed]
Many of these symptoms may be side effects of the drug or drug interaction causing excessive levels of serotonin rather than an effect of elevated serotonin itself. Tremor is a common side effect of MDMA's action on dopamine, whereas hyperreflexia is symptomatic of exposure to serotonin agonists.
Carcinoid syndrome is a rare condition characterized by an abnormal increase in circulating biologically active hormones, largely serotonin, with early symptoms involving diarrhea, abdominal cramping and episodic flushing. [7] Excess circulating serotonin is usually manufactured by EC-cell-originated carcinoid tumors in the small bowel or appendix.
An example is carcinoid syndrome, a disease in which neuroendocrine tumors along the GI tract use tryptophan as the source for serotonin production, which limits the available tryptophan for niacin synthesis. In normal patients, only one percent of dietary tryptophan is converted to serotonin; however, in patients with carcinoid syndrome, this ...