What Are Catecholamines?
Catecholamines are a group of chemically related neurotransmitters and hormones that are derived from the amino acid tyrosine. The primary catecholamines are dopamine, norepinephrine (noradrenaline), and epinephrine (adrenaline).
Biosynthesis
The synthesis of catecholamines occurs mainly in the adrenal medulla and the central nervous system. The pathway involves the following steps:
- Tyrosine → (via tyrosine hydroxylase) → L-DOPA
- L-DOPA → (via DOPA decarboxylase) → Dopamine
- Dopamine → (via dopamine β-hydroxylase) → Norepinephrine
- Norepinephrine → (via phenylethanolamine N-methyltransferase) → Epinephrine
Functions
- Dopamine: Functions as a neurotransmitter involved in movement, motivation, and reward.
- Norepinephrine: Acts as both a neurotransmitter and hormone; important for attention, alertness, and stress response.
- Epinephrine: A hormone that prepares the body for ‘fight or flight’ during stress, increasing heart rate, blood pressure, and energy supply.
Clinical Significance
- Abnormal levels of catecholamines are associated with disorders such as Parkinson’s disease (dopamine deficiency), anxiety, and hypertension.
- Urinary catecholamine levels are often measured to diagnose pheochromocytoma, a tumor of the adrenal gland.
In summary, catecholamines play vital roles in the body’s physiological and psychological responses and are central to neurochemical signaling and stress regulation.