TH and Sepsis: In the initial stage of sepsis, a large amount of IFN‐γ is released, which can promote the activation of GTP‐cyclohydrolase 1 and increase the production of 5,6,7,8‐tetrahydrobiopterin (BH4), a cofactor for phenylalanine hydroxylase (PAH), tyrosine hydroxylase (TH), and tryptophan hydroxylase (TPH), thus affecting the metabolic pathways of phenylalanine, tyrosine, and tryptophan biosynthesis (Hu et al.