At a glance
Also known as
Whole blood 5-hydroxy tryptamine; Whole blood 5-HT
Why get tested?
To help diagnose a serotonin-secreting
When to get tested?
When you have symptoms suggestive of a carcinoid tumour such as flushing, diarrhoea, and/or wheezing
A blood sample drawn from a vein in your arm
What is being tested?
This test measures the amount of serotonin in the blood. Serotonin is a chemical derived from the tryptophan. It is produced as needed by the nervous system, mainly the brain, but also by special cells in the bronchial tubes (lungs) and gastrointestinal tract. In the blood, more than 90% of serotonin is found in the platelets. Serotonin helps transmit nerve impulses and constrict blood vessels, is a participant in the wake-sleep cycle, and affects mood. Serotonin is metabolised by the liver and its , primarily 5HIAA (5-hydroxyindoleacetic acid), are excreted in the urine.
Normally, serotonin is present in small varying quantities in the blood. Large quantities of serotonin and 5HIAA may be produced continuously or intermittently by some . Carcinoid tumours are slow-growing masses that can form in the gastrointestinal tract, especially in the appendix, and in the lungs. They are one of several types of tumours that arise from cells in the - cells that are found in organs throughout the body and that have both nerve and aspects. The serotonin produced by carcinoid tumours may cause symptoms such as flushing of the face, diarrhoea, a rapid heart rate, and wheezing, especially when the tumour has spread to the liver. This group of symptoms is referred to as the carcinoid syndrome.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm. Serotonin in the blood is mainly tranpsorted in the platelets, so platelet serotonin is usually measured from the blood sample.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed