The language of medicine

Both names mean the same thing in different languages: "the stuff that comes from on top of the kidney" — the adrenal glands, which sit like little hats atop each kidney. Adrenaline is the Latin-root name (common everywhere except US pharmacology); epinephrine is the Greek-root name (the official US generic name).

The "nor-" prefix is a chemistry convention, not Greek or Latin — it indicates that one methyl group has been removed from the parent molecule. Noradrenaline is structurally adrenaline minus a methyl group; biochemically, it's the precursor. Functionally, it's the primary neurotransmitter of the sympathetic nervous system — adrenaline is the systemic hormone version released from the adrenal medulla into the blood.

Pure chemistry abbreviation — "the amine made from DOPA." DOPA itself is the chemist's shorthand for an amino acid that gets enzymatically converted into dopamine, then noradrenaline, then adrenaline. The resemblance to "dope" is coincidence — the name was coined in 1959, long before recreational connotations.

"The tone-causing thing in serum." Isolated in 1948 from blood serum by Italian researchers Vittorio Erspamer and Maurizio Asero, who noticed it constricted vascular muscle — raised the "tone" of blood vessels. The CNS function (mood, sleep, gut motility) was discovered later. The technical name is 5-HT = 5-hydroxytryptamine, which itself decomposes as 5-hydroxy (a chemical modification) + tryptamine (from tryptophan, the amino-acid precursor).

"The acetyl version of choline." Choline was named in 1862 because it was first isolated from bile (chole — same root as cholera, cholesterol, cholecystitis). Acetylcholine is the primary parasympathetic neurotransmitter and runs every neuromuscular junction in the body.

The brain's main inhibitory neurotransmitter. Named purely from its molecular structure: a butyric acid with an amino group at the gamma carbon. No etymology to enjoy — sometimes chemistry just wins.

"The amine found in tissues." Same histos as in histology (study of tissues). Histamine drives allergic responses; antihistamines block it.

"Morphine produced within" — the body's endogenous opioid. The word morphine itself is from Morpheus, the Greek god of dreams (son of Hypnos, sleep). Pain relief from inside the body, named after a god.

Named for the cells that produce it — the islets of Langerhans, microscopic "islands" of endocrine tissue scattered through the pancreas (otherwise an exocrine organ that secretes digestive juice). The hormone is from the islands; the islands were named in 1869 by Paul Langerhans. Same insula as in peninsula (almost-island) and isolate.

"The glucose-driver." Discovered in 1923 as the pancreatic hormone that does the opposite of insulin — pushes blood glucose up by releasing it from the liver. Same agon as in agonist ("the one who acts/contends") and antagonist.

"Shield-shaped." The thyroid gland really does look like a small oblong shield wrapped around the front of the trachea — the name was applied by Thomas Wharton in 1656. Thyroxine is just "thyroid" + "oxy" (oxygen) + "−ine."

Named for their tissue of origin: the adrenal cortex, the outer "bark" of the adrenal gland. (Latin cortex literally means tree bark.) Same root as cerebral cortex, cortical, decorticate. The chemical name for cortisol is 11β,17,21-trihydroxypregn-4-ene-3,20-dione — "cortisol" is the mercifully short version.

This one is grim. The pituitary — today known as the master gland of the endocrine system — was named in the 1600s because anatomists believed it produced nasal mucus. Andreas Vesalius described it as "the gland in which slime drips." We now know it secretes the hormones that control most other endocrine glands. The name never updated.

"Swift birth." First identified in 1906 as the hormone that triggers uterine contractions during labor. Later found to drive milk let-down, pair bonding, and social attachment. Same oxys as in oxygen ("acid-former" — an 18th-century misnomer) and paroxysm.

Named for the melanophores — pigment cells in amphibian skin that the substance was first shown to affect (it makes them aggregate, lightening the skin). The "−tonin" ending was borrowed from serotonin, since they share the precursor tryptophan. In humans, melatonin is the sleep-and-darkness hormone from the pineal gland. Same melas as in melancholy ("black bile") and melanoma.

A pea-sized gland buried deep in the brain that genuinely looks like a tiny pine cone — hence the name. Produces melatonin. Descartes thought it was the seat of the soul; he was wrong but the name stuck.

Testosterone: from the testicle (Latin testis, originally "witness" — ancient Romans swore oaths on them, hence "testify"). Estrogen: literally "producer of oistros" — the Greek word for the wild frenzy a cow gets when stung by a gadfly. It became the technical term for animal heat / estrous cycle, and from there for the hormone that drives it.