The three main stress hormones are cortisol, adrenaline (epinephrine), and noradrenaline (norepinephrine). All three are produced by your adrenal glands, the small triangle-shaped glands that sit on top of each kidney. They work together during stressful situations, but each one has a distinct job and operates on a different timeline.
Where Each Hormone Comes From
Your adrenal glands have two distinct layers, and the stress hormones are split between them. Cortisol is produced in the outer layer, called the adrenal cortex, specifically in a zone called the zona fasciculata. Adrenaline and noradrenaline are both produced in the inner core, called the adrenal medulla. This anatomy matters because it explains why the hormones behave so differently: cortisol is a slow-acting steroid hormone, while adrenaline and noradrenaline are fast-acting chemical messengers called catecholamines.
Cortisol: The Sustained Stress Hormone
Cortisol is often called the body’s primary stress hormone because its effects are the broadest and longest-lasting. When you’re under stress, cortisol triggers your liver to release stored glucose into your bloodstream, giving your body a rapid supply of energy. It also signals your pancreas to decrease insulin (which lowers blood sugar) and increase glucagon (which raises it), keeping that fuel available for as long as the stressor lasts. Beyond the liver, cortisol acts on body fat and muscle tissue to further manage how energy gets used.
Cortisol also plays a role in your immune system. In short bursts, it actually boosts immunity by limiting inflammation. But when cortisol stays elevated for long periods, your body adapts to the constant exposure. That adaptation can backfire, leading to increased inflammation and a weakened immune response, the opposite of what happens during brief, healthy stress.
Cortisol levels follow a natural daily rhythm. They peak in the early morning to help you wake up. A blood sample taken at 8 a.m. typically falls between 5 and 25 mcg/dL. Levels drop throughout the day and reach their lowest point around midnight. When chronic stress disrupts this cycle, cortisol can remain elevated at times when it should be low, which interferes with sleep and recovery.
Adrenaline: The Immediate Alarm Signal
Adrenaline is the hormone most people associate with the “fight or flight” response, and for good reason. It acts within seconds. When adrenaline surges, your heart pumps harder and faster to deliver oxygenated blood to the muscles that need it most. Blood pressure rises. Your airways open wider and breathing becomes deeper and faster, pushing more oxygen into your bloodstream.
This is the hormone responsible for that racing-heart, heightened-awareness sensation you feel during a sudden scare or intense moment. It also redirects blood flow away from less urgent functions, like digestion, and toward your muscles and brain. The effects are powerful but short-lived. Once the threat passes, adrenaline levels drop quickly, which is why you may feel shaky or drained after a stressful event.
Adrenaline binds strongly to receptors that dilate your airways and increase your heart rate. This is why synthetic adrenaline is used in emergencies like severe allergic reactions: it relaxes airway muscles and counteracts the dangerous swelling that restricts breathing.
Noradrenaline: Focus and Blood Flow
Noradrenaline works alongside adrenaline but has a slightly different emphasis. While adrenaline is more about whole-body activation, noradrenaline plays a bigger role in alertness, attention, and blood vessel constriction. It narrows blood vessels to help maintain blood pressure during stress and sharpens focus so you can assess a threat.
In the brain, noradrenaline increases during stress and affects the prefrontal cortex, the region involved in decision-making and working memory. At moderate levels, this sharpens your thinking. But at very high levels, such as during extreme or prolonged stress, noradrenaline can actually impair working memory, attention regulation, and impulse control. This helps explain why people sometimes make poor decisions or feel mentally foggy during overwhelming situations.
The receptor profile of noradrenaline differs from adrenaline in important ways. Noradrenaline binds strongly to receptors that constrict blood vessels and stimulate the heart, but it binds very poorly to the receptors that open airways. Adrenaline, by contrast, activates airway-opening receptors much more effectively. This is why the two hormones complement each other: noradrenaline keeps blood pressure up and attention sharp, while adrenaline ensures your heart, lungs, and muscles are firing at full capacity.
How the Three Hormones Work Together
The stress response unfolds in stages, and each hormone has its window. Adrenaline and noradrenaline hit first, surging within seconds to produce the immediate physical response: faster heartbeat, rapid breathing, heightened awareness. Cortisol takes longer to kick in, typically peaking minutes after the stressor begins, but its effects last much longer. It sustains the energy supply and manages inflammation while your body stays in a heightened state.
In a healthy stress response, all three hormones spike, do their jobs, and return to baseline once the threat is gone. Problems arise when the stressor doesn’t go away. Chronic work pressure, ongoing financial strain, or persistent anxiety can keep these hormones circulating at elevated levels. The consequences of that sustained elevation include disrupted sleep, weakened immunity, higher blood sugar, and increased inflammation.
DHEA: A Protective Counterbalance
Your adrenal glands also produce a hormone called DHEA, which acts as a natural counterweight to cortisol. DHEA is produced in a different section of the adrenal cortex than cortisol, but both are released in response to the same brain signal. DHEA has regenerative and protective properties, and it functions as an antagonist to cortisol’s more damaging effects.
The ratio between cortisol and DHEA matters more than the level of either one alone. A high cortisol-to-DHEA ratio has been linked to chronic stress, depression, and cognitive problems. People who report high levels of perceived stress at work tend to have a blunted DHEA response during acute stress, meaning their built-in buffer against cortisol’s harmful effects is weakened precisely when they need it most.