Aspects of tryptophan metabolism in health and disease: a review.

Abstract

Some of the more recent developments in the study of tryptophan metabolism are reviewed with the intent of demonstrating that abnormalities associated with abnormal tryptophan metabolism may result from the influence of hormonal and nutritional factors upon the metabolic pathway. It has been shown that pregnancy and treatment with estrogens or estrogen-containing oral contraceptives (OCs) all produce elevated urinary excretion of tryptophan metabolites; administration of pyridoxine will normalize urinary levels. The effect of estrogens upon tryptophan oxygenase appears to be indirect mediated via the adrenals. The clinical significance of changes following OC use is unknown but evidence of an occult Vitamin-B6 deficiency is being sought. It is possible that OC/tryptophan-associated depression results when a patient lacks a compensatory biochemical mechanism that normally counters any reduction in the level of brain 5-hydroxytryptamine. In any event it is important to exclude all patients receiving estrogens from studies which attempt to demonstrate an association between abnormal tryptophan metabolism and a specific disease.