Serotonin (5-hydroxytryptamine) belongs to the group of biogenic amines and is an intermediate product of the tryptophan metabolism. It plays an important role as a neurotransmitter in the regulation of different behavioural patterns such as motor activity, aggression, sexuality, appetite, depressions, and sleep.

Serotonin can be found in the intestinal mucosa, in urine, and in blood as well as in the central nervous system (CNS). In blood, it is transported predominantly in the platelets.

Diseases which are associated with altered serotonin concentrations include disorders of the CNS, for example autism, epilepsy, schizophrenia and depression, and carcinoid tumors of the intestine or bronchi.

For the determination of Serotonin in serum and urine LDN offers  an enzyme immunoassay. The assay is intended for in-vitro diagnosis and research applications.