Adrenochrome is what adrenaline becomes when it oxidizes: a compound with the formula C9H9NO3, deep violet as a solid and pink in solution. The "chrome" in the name refers to color, not chromium. It has been synthesized in laboratories since at least 1952, and chemical suppliers sell it for research. A derivative, carbazochrome, is used as a medicine to slow bleeding.
In 1952 the psychiatrists Humphry Osmond and John Smythies pointed out that mescaline and adrenaline are chemically similar, and suggested the body might make a hallucinogen of its own. Working in Saskatchewan with Abram Hoffer, they settled on adrenochrome and published the idea in 1954. Hoffer later named it the adrenochrome hypothesis of schizophrenia and treated patients with large doses of niacin and vitamin C. Later studies did not confirm a benefit, and the hypothesis faded. Writers got more out of it than doctors did. Aldous Huxley mentioned it in The Doors of Perception (1954), Anthony Burgess put "drencrom" in the milk in A Clockwork Orange (1962), and in Hunter S. Thompson's Fear and Loathing in Las Vegas (1971) a character says the only source is "the adrenaline glands from a living human body".
The modern story keeps Thompson's detail and drops the fiction. In 2016 the Pizzagate rumor claimed that a child-abuse ring was run from a Washington, D.C. pizzeria. QAnon, which began on the message board 4chan in October 2017, absorbed that rumor, and its followers added adrenochrome: a drug or youth serum that Hollywood and political elites supposedly harvest from frightened children. No evidence for any of it has surfaced. Writers who have traced the story point to Thompson's novel as the likely seed, and note how closely it repeats blood libel: the medieval accusation that Jews murdered Christian children for their blood.