The TPH2 gene encodes the important enzyme, tryptophan hydroxylase 2 that makes serotonin. TPH2 is produced most significantly in the brain stem. The encoded protein catalyses the first and rate-limiting step in the biosynthesis of serotonin, an important hormone, and neurotransmitter.
The G-allele is considered to be the risk allele in this gene and may be associated with depression, bipolar affective disorder and major depression.
It is important to consider your genetic variation in this gene with that of your COMT and BDNF genotypes.