DBH (dopamine beta-hydroxylase) encodes a copper-dependent enzyme that catalyzes the conversion of dopamine to norepinephrine, serving as the rate-limiting step in norepinephrine biosynthesis 1. The enzyme is highly expressed in the locus coeruleus and adrenal glands, with additional expression in sympathetically innervated organs including liver, lung, and heart 1. DBH functions through regulatory polymorphisms, particularly rs1611115 and rs1108580, which significantly affect mRNA expression levels in peripheral tissues and modulate sympathetic tone 1. These variants show profound tissue-specific effects, with 2- to 11-fold allelic expression differences in liver but minimal differences in brain regions 1. The gene's clinical significance extends to multiple disorders: variants are associated with cardiovascular phenotypes including potential protection against myocardial infarction 1, migraine susceptibility 2, and renal function through genetic covariance with norepinephrine secretion 3. DBH polymorphisms also influence neuropsychiatric conditions, with lower enzyme activity linked to PTSD susceptibility 4 and variants affecting attention-related phenotypes 5. The enzyme's role in maintaining dopamine-to-norepinephrine ratios makes it crucial for sympathetic nervous system function and multiple disease pathways 2.