5-HIAA

5-Hydroxyindoleacetic acid

Names
IUPAC name 2-(5-Hydroxy-1H-indol-3-yl)acetic acid
Identifiers
CAS Number	54-16-0 Y
3D model (Jmol)	Interactive image
ChEBI	CHEBI:27823 Y
ChemSpider	1760 Y
ECHA InfoCard	100.000.179
KEGG	C05635 Y
MeSH	Hydroxyindoleacetic+Acid
PubChem CID	1826
InChI InChI=1S/C10H9NO3/c12-7-1-2-9-8(4-7)6(5-11-9)3-10(13)14/h1-2,4-5,11-12H,3H2,(H,13,14) Y Key: DUUGKQCEGZLZNO-UHFFFAOYSA-N Y InChI=1/C10H9NO3/c12-7-1-2-9-8(4-7)6(5-11-9)3-10(13)14/h1-2,4-5,11-12H,3H2,(H,13,14) Key: DUUGKQCEGZLZNO-UHFFFAOYAY
SMILES c1cc2c(cc1O)c(c[nH]2)CC(=O)O
Properties
Chemical formula	C10H9NO3
Molar mass	191.19 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y  (what is YN ?)
Infobox references

5-Hydroxyindoleacetic acid (5-HIAA) is the main metabolite of serotonin. In chemical analysis of urine samples, 5-HIAA is used to determine serotonin levels in the body.

5-HIAA is tested by 24-hour urine samples combined with an acidic additive to maintain pH below 3. Certain foods and drugs are known to interfere with the measurement. 5-HIAA levels can vary depending on other complications, including tumors, renal malfunction, and small bowel resection.

Since 5-HIAA is a metabolite of serotonin, testing is most frequently performed for the diagnosis of carcinoid tumors of the enterochromaffin (Kultschitzsky) cells of the small intestine, which release large amounts of serotonin. Values greater than 25 mg per 24 hours (higher if the patient has malabsorption) are strong evidence for carcinoid. The normal range is 2 to 6 mg per 24 hours.

Low levels of 5-HIAA in the cerebrospinal fluid have been associated with aggressive behavior and suicide by violent means, correlating with diminished serotonin levels.

Elevated serotonin (hyperserotonemia) is one of the most common biological findings in autism and 5-HIAA may be elevated in patients with autistic spectrum disorders.

5-HIAA may be normal with nonmetastatic carcinoid tumor and may be normal even with the carcinoid syndrome, particularly in subjects without diarrhea, because some patients with the carcinoid syndrome excrete nonhydroxylated indolic acids.

The production and metabolism of serotonin, and thus 5-HIAA, is dependent upon the tissue of origin of the tumor. Tumors from midgut cells, such as ileal carcinoid usually contain and release large quantities of serotonin. These amounts may not be fully reflected in the amount of 5-HIAA in urine, because little is metabolized. Foregut tumors lack the decarboxylase enzyme necessary to convert 5-hydroxytryptophan to serotonin, resulting in minimal to no elevation in urinary 5-HIAA levels. Tumors derived from hindgut cells (rectal carcinoid) rarely produce excess serotonin or 5-HIAA. Of 75 patients with carcinoid tumors, 75% had above normal urinary 5-HIAA excretion and 64% had above normal serotonin excretion.