The main hormone released during stress is cortisol, often called the “stress hormone.” But cortisol isn’t the only one. Your body actually launches two separate hormonal waves when you encounter a threat: first adrenaline (epinephrine) fires within seconds, then cortisol follows minutes later. Together, these hormones prepare your body to fight, flee, or endure whatever challenge you’re facing.
The First Wave: Adrenaline
The moment your brain registers a threat, your sympathetic nervous system activates what’s known as the fight-or-flight response. This triggers your adrenal glands to release adrenaline (epinephrine) and noradrenaline (norepinephrine) within seconds. These are the hormones responsible for the immediate physical sensations of stress: your heart pounds, your breathing quickens, your muscles tense, and your pupils dilate. Blood flow shifts away from digestion and toward your muscles and brain, giving you the burst of energy and alertness needed to respond to danger.
This reaction is fast and short-lived by design. Adrenaline spikes rapidly and drops off quickly once the perceived threat passes. It’s why your hands might shake after a near-miss car accident but feel normal again 10 or 15 minutes later.
The Second Wave: Cortisol
While adrenaline handles the first few seconds, your body simultaneously sets a slower hormonal chain in motion. Your hypothalamus, a small region at the base of your brain, releases a signaling hormone called CRH. That hormone travels to your pituitary gland, which responds by releasing another signaling hormone called ACTH. ACTH then travels through your bloodstream to your adrenal glands, which sit on top of your kidneys, prompting them to produce cortisol.
This relay system, called the HPA axis, takes longer to activate than adrenaline but produces effects that last much longer. Cortisol raises blood sugar to fuel your brain and muscles, suppresses non-essential functions like immune activity and digestion, and helps maintain blood pressure. It’s the hormone that keeps your body in a heightened state of readiness beyond the initial adrenaline surge.
Under normal conditions, cortisol has a built-in off switch. Once levels rise high enough, cortisol signals your hypothalamus to stop producing CRH, which shuts down the entire chain. This negative feedback loop is what brings your body back to baseline after the stressor passes.
How Cortisol Levels Change Throughout the Day
Cortisol doesn’t only show up during stressful moments. It follows a natural daily rhythm, peaking in the early morning and declining through the afternoon and evening. Normal blood cortisol levels typically range from 10 to 20 micrograms per deciliter between 6 a.m. and 8 a.m., then drop to 3 to 10 mcg/dL by around 4 p.m. This morning surge is what helps you wake up and feel alert.
Stress pushes cortisol above these baseline levels. A single stressful event can cause a temporary spike that resolves within an hour or two. The problem arises when stressors are constant, because cortisol levels stay elevated instead of cycling back down.
Other Hormones Involved in Stress
Adrenaline and cortisol get the most attention, but your brain also releases other hormones that shape how you experience and cope with stress. Two notable ones are vasopressin and oxytocin, both produced in the hypothalamus. These hormones are released in response to stressful and social situations, both positive and negative, and they play opposing roles in how you feel.
Oxytocin tends to reduce anxiety and promote a more active style of coping with stress. It’s sometimes called the “bonding hormone” because it’s released during social connection, physical touch, and caregiving. Vasopressin, on the other hand, tends to increase anxiety and promote more passive, withdrawn responses to stress. The balance between these two hormones helps explain why social support can be so powerful during difficult times: connection may literally shift your brain chemistry toward calmer, more resilient responses.
What Happens When Stress Doesn’t Stop
The stress hormone system is designed to turn on quickly and turn off quickly. Problems develop when the system stays activated for weeks, months, or years. Chronic exposure to elevated cortisol and other stress hormones disrupts nearly every system in the body.
The health consequences are broad and well documented. Prolonged stress increases the risk of heart disease, high blood pressure, heart attack, and stroke. It contributes to weight gain, particularly around the midsection, because cortisol promotes fat storage and increases appetite. Digestive problems are common, ranging from stomachaches to more serious conditions. Sleep suffers because elevated evening cortisol interferes with the natural wind-down your body needs. Memory and concentration decline as well, since the brain regions responsible for learning are sensitive to sustained cortisol exposure. Anxiety, depression, chronic headaches, and persistent muscle tension round out a list that touches almost every part of daily life.
The pattern that drives these effects is straightforward: the negative feedback loop that normally shuts off cortisol production stops working properly. Your hypothalamus becomes less sensitive to the “stop” signal, so cortisol keeps flowing even when no immediate threat exists. Over time, your baseline cortisol level creeps upward, and the body adapts to operating in a state of low-grade emergency. This is why managing chronic stress matters so much. The hormones that protect you in a crisis can slowly damage your health when they never fully turn off.