Used as a biomarker for immune system activation, particularly in monitoring inflammatory and infectious diseases. Elevated levels are associated with conditions such as viral infections, autoimmune disorders, and sepsis. It is also studied in relation to oxidative stress and endothelial dysfunction, making it relevant in cardiovascular and neurodegenerative disease research. Due to its role in the pteridine pathway, it serves as a precursor in the biosynthesis of tetrahydrobiopterin (BH4), a critical cofactor for enzymes involved in neurotransmitter synthesis and nitric oxide production. Its detection in biological fluids like urine and plasma supports diagnostic and prognostic evaluations in clinical settings.