catecholamine
Meaning of catecholamine: The chemical family behind the surge of a fright, named for a ring of carbon that every member shares.
Definition of catecholamine
A catecholamine is any of a small group of signaling molecules built on the same chemical skeleton: a six-carbon ring carrying two neighboring hydroxyl groups, joined to a short chain ending in an amine. The three the body makes are dopamine, norepinephrine and epinephrine. They serve as messengers between nerve cells and, when released from the adrenal glands into the blood, as hormones.
Where do they come from?
All three are built along one assembly line from a single amino acid in food. The first step is the slowest, converting that amino acid into a compound called L-DOPA, and because it sets the pace it is the step the body regulates. L-DOPA becomes dopamine, dopamine becomes norepinephrine, and norepinephrine becomes epinephrine. Different cells stop at different points depending on what they need. Nerve endings in the brain that use dopamine stop at the third step. Sympathetic nerve endings around the body continue to norepinephrine. Only the inner core of the adrenal gland carries much of the final enzyme, which is why adrenaline, the other name for epinephrine, is overwhelmingly a hormone poured into the blood rather than a nerve signal.
What does each one do?
| Molecule | Acts chiefly as | Prominent effects |
|---|---|---|
| Dopamine | Brain messenger | Movement, motivation, reward, control of other hormones |
| Norepinephrine | Nerve messenger | Tightens vessels, sharpens alertness, lifts blood pressure |
| Epinephrine | Adrenal hormone | Speeds the heart, opens airways, releases stored sugar |
The label neurohormone gets applied loosely to the whole group, but the three are not interchangeable. Dopamine barely leaves the compartment it works in. Epinephrine circulates widely. Norepinephrine does both. The name of the family is chemical rather than biological: catechol is the name of that double-hydroxyl ring, and the amine is the nitrogen-bearing tail attached to it.
Why are they measured?
Because a tumor of the adrenal core, or of related nerve tissue, can release them in bursts. The classic picture is spells of pounding heartbeat, headache, heavy sweating and severe high blood pressure that arrive and then pass. Skin during an attack is characteristically pale rather than flushed, because vessels near the surface clamp shut, and sources describing facial flushing have this the wrong way round. Testing usually measures the breakdown products in blood or urine rather than the molecules themselves, since the parent compounds survive only minutes while their remnants leak out steadily whether or not a spell is under way.
Also known as
Used in a sentence
Catecholamine breakdown products were measured in a twenty-four hour urine collection.
Good to know
Tumors that release catecholamines classically cause pallor during an attack rather than flushing, and testing measures the longer-lived breakdown products because the hormones themselves persist in the blood only minutes.