5-Hydroxytryptamine metabolism in coeliac disease

Abstract

Interest in 5-hydroxytryptamine (5-HT) metabolism in children with coeliac disease began with the finding of increased urinary excretion of 5-hydroxy-indoleacetic acid (5-HIAA) in adults with this disorder (Haverback and Davidson, 1958; Kowlessar et al., 1958). 5-HT is synthesized from dietary tryptophan by enterochromaffin (EC) cells in the gastrointestinal tract and is broken down by the enzyme monoamine oxidase (MAO) to 5-HIAA, which is excreted in the urine. Raised blood levels of 5-HT have been reported in patients with untreated coeliac disease (Pimparker et al., 1961; Warner and Cohen, 1962), and both blood 5-HT and urinary 5-HIAA levels fell to normal after the introduction of a gluten-free diet (Sleisenger, 1961). Increased urinary excretion of 5-HIAA and diminished excretion following a gluten-free diet were confirmed in children with coeliac disease, in 24 and 8 hour urine collections (Challacombe et al., 1972; Challacombe et al., 1975), and measurement of 8 hour urinary 5-HIAA was proposed as an aid to diagnosis. The possible origins of these abnormalities of 5-HT metabolism in the small intestine of patients with coeliac disease were therefore studied.