Catecholamine is the common term for the important hormones Norepinephrine (Noradrenaline), Epinephrine (Adrenaline) and Dopamine. Chromaffin cells of the adrenal medulla are the key site of catecholamine synthesis and collections of these cells are also found in heart, liver, kidney, gonads, adrenergic neurons of the postganglionic sympathetic system, and CNS (Central Nervous System). The major product of the adrenal medulla is epinephrine, which constitutes 80% of the catecholamines released from the medulla.
Tyrosine initiates catecholamine biosynthesis. It is produced in the liver from phenylalanine through the action of phenylalanine hydroxylase. The tyrosine is then transported to catecholamine-secreting neurons where a series of reactions convert it to dopamine, norepinephrine and finally to epinephrine. Hydroxylation of tyrosine and consecutive decarboxylation yields dopamine. TH [...]