Recently searched HealthUnlocked for "kyneurenine" and was surprised to find no hits. People on the anxiety & depression forum need to determine if tryptophan metabolism is related to their anxiety and/or depression. If you have this condition, it is *very* unlikely that your shrink, or any other allopathic doctor, will diagnose or treat it.
Tryptophan has two metabolic pathways: (1) creating serotonin & melatonin, the desired pathway. (2) creating kynurenine, a pathway which promotes stress hormones and creates substances toxic to the body. Staying on pathway (1) is problematic if you have nutritional deficiencies (B3, B5, B6, SAM (methionine), iron), and/or you have conditions like inflammation, autoimmunity, and/or a gut disorder (Crohn's, Celiac, etc.).
In some cases, targeted vitamin/mineral therapy with multi-gram level doses of free tryptophan can correct the condition. However, difficult cases may not be treatable this way.
The following youtube videos will help you understand this disorder.
serotonin-melatonin pathway:
youtube.com/watch?v=kCkZBSe...
kyneurenine pathway: