tetrahydrobiopterin biosynthetic process The chemical reactions and pathways resulting in the formation of tetrahydrobiopterin, the reduced form of biopterin (2-amino-4-hydroxy-6-(1,2-dihydroxypropyl)-pteridine). It functions as a hydroxylation coenzyme, e.g. in the conversion of phenylalanine to tyrosine. tetrahydrobiopterin anabolism 5,6,7,8-tetrahydrobiopterin biosynthetic process tetrahydrobiopterin biosynthesis biological_process GO:0006729 tetrahydrobiopterin synthesis tetrahydrobiopterin formation diol biosynthetic process pteridine-containing compound biosynthetic process tetrahydrobiopterin metabolic process