As nouns the difference between epinephrine and tetrahydrobiopterin

is that epinephrine is (hormone|neurotransmitter|organic compound) a catecholamine hormone and neurotransmitter; as a hormone, secreted by the adrenal gland in response to stress (when it stimulates the autonomic nervous system); as a neurotransmitter, synthesized from norepinephrine while tetrahydrobiopterin is (biochemistry) a naturally-occurring nutrient and essential cofactor of the three aromatic amino acid hydroxylase enzymes, used in the biosynthesis of the neurotransmitters serotonin, melatonin, dopamine, norepinephrine, epinephrine, and nitric oxide.