At present, no specific enzyme deficiency nor genetic mutation has been implicated as the cause of<unk> . Several known factors regarding tryptophan metabolism and kynurenines, however, may explain the presence of behavioral abnormalities seen with the disorder. Tryptophan is an essential amino acid, and is required for protein synthesis. Aside from this crucial role, the remainder of tryptophan is primarily metabolized along the kynurenine pathway in most tissues, including those of the brain and central nervous system. As the main defect behind<unk>  is suspected to alter and disrupt the metabolic pathway from tryptophan to kynurenine, a possible correlation between<unk>  and the known effects of kynurenines on neuronal function, physiology and behavior may be of interest. One of these kynurenines, aptly named kynurenic acid, serves as a neuroprotectant through its function as an antagonist at both nicotinic and glutamate receptors (responsive to the neurotransmitters nicotine and glutamate, respectively). This action is in opposition to the agonist quinolinic acid, another kynurenine, noted for its potential as a neurotoxin. Quinolinic acid activity has been associated with neurodegenerative disorders such as Huntington's disease, the neuroprective abilities of kynurenic acid forming a counterbalance against this process, and the related excitotoxicity and similar damaging effects on neurons. Indoleic acid excretion is another indicator of<unk> . Indirectly related to kynurenine metabolism, indole modifies neural function and human behavior by interacting with voltage-dependent sodium channels (integral membrane proteins that form ion channels, allowing vital synaptic action potentials).
Hypertryptophanemia
Hyperphenylalaninemia
Hypervalinemia
Hypermethioninemia
Hyperlysinemia
Histidinemia
Hyperprolinemia
Hyperprolactinaemia