Clinical use: To diagnose and monitor treatment for a serotonin secreting carcinoid tumour.
Background: This test measures the amount of 5-hydroxyindoleacetic acid (5-HIAA) in the urine. 5-HIAA is a muscle stimulant and the primary metabolite of serotonin, a hormone derived from the amino acid tryptophan. Serotonin is produced as needed by the nervous system, mainly the brain, but also special cells in the bronchial tubes (lungs) and gastrointestinal tract. It helps transmit nerve impulses and constrict blood vessels, participates in the wake-sleep cycle, and affects mood.After it has been used by the body, serotonin is broken down in the liver, and its metabolites, including 5-HIAA, are excreted in the urine. Large quantities of serotonin and 5-HIAA may be produced however, by some carcinoid tumours. Carcinoid tumours are slow-growing masses that can form in the gastrointestinal tract, on the appendix and in the lungs.

About 10% of carcinoid tumours, primarily those found in the gastrointestinal tract, will produce enough serotonin to cause symptoms such as flushing of the face, diarrhoea, a rapid heart rate, and wheezing, usually only after the tumour has spread to the liver. These symptoms are referred to as the carcinoid syndrome.

The serotonin that causes the carcinoid syndrome may be released continuously or intermittently and can lead to significantly increased quantities of 5-HIAA in the urine.

Reference ranges:
  • 0 – 40 umol/24h
  • Borderline: 40 – 78 umol/24h
  • Carcinoid Range: 130+ umol/24h
Associated diseases:
Patient preparation:

24 Hour Urine 5HIAA Patient Information Sheet (62.6kb)
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Specimen requirements: A 24hr urine sample in a urine container with a measured amount of acid (6mL of 4M Sulphuric Acid) and sand (20g) is required.
Turnaround time: 1 week
Additional information:
Referred Test: Referred test
Location: Freeman Hospital