NoradrenalineNorepinephrine

Noradrenaline, called norepinephrine in American sources, is both a neurotransmitter and a hormone. Sympathetic nerve endings release it directly onto tissues, and the adrenal glands release a smaller amount into the bloodstream, where it acts more slowly and for longer.

Its effects are the familiar mobilising ones: heart rate and contractility rise, blood vessels in the periphery constrict, blood pressure rises, and glucose and fatty acids are released into circulation. It is the workhorse of the sympathetic nervous system.

It differs from adrenaline in emphasis rather than in kind. Noradrenaline is more about vascular tone and sustained readiness; adrenaline, released mainly from the adrenal glands, produces the sharper whole body surge people recognise as a fright response.

In the brain it is a major neurotransmitter for arousal, vigilance and attention, which is why several medications for attention deficit disorder and some antidepressants act on it, and why caffeine's alerting effect partly runs through the same system.

During exercise it rises with intensity and duration, contributing to fuel mobilisation and to the acute alertness of hard training. Chronically elevated sympathetic activity is the other side of that coin and shows up as a raised resting heart rate, suppressed heart rate variability and poor sleep.

There is nothing useful to buy here. Products claiming to modulate noradrenaline in healthy people are generally stimulants with the usual trade-offs, and the meaningful levers are sleep, training load and stress.

In practice, treat persistent signs of sympathetic dominance as a load management problem rather than a hormone problem, and read them against your own baseline with our recovery readiness index.