Definition
Adrenaline, also called epinephrine, is a hormone released by the adrenal medulla in response to perceived threat. It's the chemical driver behind most of the fast physical symptoms of anxiety and panic.
What it can feel like
A flush of warmth, then cold. A sudden heartbeat in the ears. Hands that tremble slightly. An urgent quality to whatever the person was just doing. After the surge passes, a tired, washed-out feeling that can last for hours.
Why it happens
Adrenaline rises within seconds of a stress signal from the brain. It increases heart rate and contractility, raises blood pressure, dilates the airways, and shifts blood flow toward the large muscles. Once released, it's metabolized within minutes. This is one reason panic attacks are time-limited: the chemistry can't sustain itself.
When to see a clinician
Adrenaline surges driven by anxiety are uncomfortable. In otherwise healthy people, once cardiac and endocrine causes have been ruled out by a clinician, the surge itself isn't a medical emergency. A first episode of unexplained palpitations or chest pain still warrants medical evaluation; the patterns described here apply once that evaluation is normal. Surges that arrive without an emotional trigger, that come with chest pain or fainting, or that recur after panic disorder has otherwise been treated, deserve a medical evaluation to rule out cardiac and endocrine causes (including pheochromocytoma in rare cases).