Kynurenine-Tryptophan Ratio

Tryptophan is a precursor of melatonin and serotonin. One way it is degraded in the body is by the enzyme indoleamine 2,3 deoxygenase — which is stimulated by inflammation — to produce kynurenine. The ratio of kynurenine to tryptophan is a measure of tryptophan degradation, with a lower value suggesting decreased tryptophan degradation.