Hyperphenylalaninemia Due to Tetrahydrobiopterin Deficiency, also known as hyperphenylalaninemia due to bh4 deficiency, is related to hyperphenylalaninemia, bh4-deficient, b and hyperphenylalaninemia, bh4-deficient, a. An important gene associated with Hyperphenylalaninemia Due to Tetrahydrobiopterin Deficiency is PTS (6-Pyruvoyltetrahydropterin Synthase), and among its related pathways/superpathways is Biogenic amine synthesis. The drug D-Phenylalanine has been mentioned in the context of this disorder.