Table 4

 Additional specific biochemical tests used in the diagnosis of neuroendocrine tumours (NETs)16,26–30

5-HIAA, 5-hydroxy indole acetic acid; GHRH, gonadotrophin releasing hormone; ACTH, adrenocorticotrophic hormone; β-HCG, β-human chorionic gonadotrophin.
Currently in the UK, the following are the hormones normally performed when gut hormones are requested: gastrin, glucagon, somatostatin, pancreatic polypeptide, vasointestinal peptide, and neurotensin. Chromogranin A will be performed on the same sample when requested. Blood is taken in a 10 ml standard heparin bottle with trasylol (aprotinin 0.2 ml, 2000 KIU) and spun immediately before being frozen and sent to one of the reference laboratories.
    Foregut24 h urinary 5-HIAASometimes raised31
    Midgut24 h urinary 5-HIAAUsually raised (70% of patients)
Tachykinins (neurokinin A and B)Raised
    Hindgut24 h urinary 5-HIAANot raised (general markers used instead)
Other NETs
    GastrinomaFasting gastrin, gastric secretion studiesRaised basal serum gastrin, high gastric acid secretion
    InsulinomaFasting insulin, glucose, C peptide (sulphonylurea
>screen negative)
Raised fasting insulin/glucose ratio, proinsulin, or C peptide
    GlucagonomaFasting gut hormones, skin biopsyRaised serum pancreatic glucagons and enteroglucagon
    VIPomaFasting gut hormonesRaised fasting vasointestinal peptide
    PpomaFasting gut hormonesRaised fasting pancreatic polypeptide
    SomatostatinomaFasting gut hormonesRaised fasting somatostatin
All NETsSerum chromograninRaised chromogranin A in most cases23–25
Ectopic hormonesGHRH, ACTH, HCG-α and -βRaised but incidence very low