A biologically active amine, derived from tyrosine, that mimics the effects of adrenaline, causing increased heart activity and raising blood pressure. It occurs naturally in body tissues and can also be found in ergot, mistletoe, putrefied animal tissue, and cheese. Certain antidepressant drugs, called monoamine oxidase inhibitors (MAO inhibitors), prevent the normal metabolism of tyramine, leading to dangerously high blood pressure. Hence people prescribed such drugs are advised not to eat cheese.