What Is Adrenaline?

Facts About the Stress Hormone, Also Known as Epinephrine

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Adrenaline, also known as epinephrine, is a type of hormone that is released whenever a person experiences fear, anxiety, or stress. It is the hormone that triggers the fight-or-flight response.

Adrenaline prepares the body to either fight or flee from danger by increasing blood circulation and breathing. While this response is crucial to survival, over-exposure to adrenaline can be damaging to a person's health.

This article looks at how adrenaline works in the body, including the symptoms of an "adrenaline rush," as well as the causes and consequences of adrenaline overproduction and adrenaline deficiency.

Senior tandem skydiving

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How Adrenaline Works 

Adrenaline works by stimulating a part of the nervous system known as the sympathetic nervous system that regulates the body's unconscious actions. It is released at times of physical and emotional stress by the adrenal glands, which are situated atop each kidney.

When adrenaline is released, it affects the body in six key ways:

  • It causes air passages to widen (dilate) to provide muscles with the oxygen they need to either fight or flee danger.
  • It causes blood vessels to narrow (contract) to redirect blood flow to major muscle groups, including the heart and lungs.
  • It causes the heart rate to speed up and the heart to contract more forcefully so that more oxygen is delivered to muscles and tissues.
  • It causes the liver to release blood sugar (glucose), which provides the body with energy.
  • It causes the pupils of your eyes to dilate (known as stress-induced mydriasis) so that you see more clearly, even in the dark.
  • It reduces the perception of pain (known as stress-induced analgesia) so that you can continue fighting or fleeing even if you are injured.

Adrenaline is not only released when there is actual danger but also during moments of emotional stress. This may include taking a test, watching a scary movie, speaking in public, going out on a date, or doing an extreme sport like skydiving.


The typical "adrenaline rush" starts immediately and can last for up to an hour after the stress subsides.

Common symptoms of an adrenaline rush include:

  • A pounding heart
  • Rapid heart rate
  • Rapid and shallow breathing
  • Increased sweating
  • Dilated pupils
  • Increased ability to run or lift heavy objects
  • Feeling shaky or nervous
  • Trembling or shaking
  • Dizziness
  • Dry mouth


There are times when the body will release adrenaline when it is under emotional stress but not facing any real danger.

When this occurs, the release of glucose into the bloodstream can accumulate rather than being burned off. This can cause symptoms like restlessness and irritability. There may also be dizziness, lightheadedness, vision changes, sweating, and a pounding heart.

Persistently high adrenaline levels caused by chronic (ongoing) psychological stress can lead to serious health concerns over time, including:

According to a 2017 study in the medical journal Lancet, emotional stress was associated with a 59% increase in the risk of a cardiovascular event in people with heart disease.

Producing too little adrenaline also has health consequences as well. While this is rare, conditions that either damage or destroy the adrenal glands (or require the removal of the adrenal glands) can lead to symptoms such as:


Medical conditions that cause the overproduction (hypersecretion) or underproduction (insufficiency) of adrenaline are uncommon but can occur. These conditions either directly or indirectly affect the adrenal glands.

Adrenal Hypersecretion

There are several conditions that can cause the adrenal glands to release too much adrenaline, referred to as adrenal hypersecretion. Chief among these are:

  • Cushing syndrome: This is a disorder that causes the overproduction of the stress hormone cortisol and the related stress hormones adrenaline and aldosterone. Adrenaline, cortisol, and aldosterone are all produced by the adrenal glands, while the release of the hormones is regulated by the pituitary gland in the brain. Common causes include the prolonged use of corticosteroid (steroid) drugs and pituitary gland tumors.
  • Adrenal gland tumors: Tumors of the adrenal glands can also cause the overproduction of adrenaline and cortisol. The tumors are usually benign (non-cancerous) but can sometimes be cancerous. A type of tumor called a pheochromocytoma affects cells responsible for producing adrenaline, leading to the overproduction of adrenaline.
  • Obstructive sleep apnea: This chronic sleep disorder, which causes the momentary disruption of breathing, can indirectly cause adrenal hypersecretion by triggering a stress response as you gasp for air. If left untreated, obstructive sleep apnea can increase the risk of high blood pressure, diabetes, and atherosclerosis due in part to chronic overproduction of adrenaline.

Adrenal Insufficiency

Adrenal insufficiency, the underproduction of adrenaline, is uncommon and rarely occurs on its own. It is the result of the adrenal glands producing too little (or no) hormones.

There are two types of adrenal insufficiency, referred to as Addison's disease and secondary adrenal insufficiency.

Addison's disease, also known as primary adrenal insufficiency, occurs when there is a problem with the adrenal glands themselves. Possible causes include:

Secondary adrenal insufficiency is caused by a problem with the pituitary gland that regulates the release of adrenaline. Causes include:

The symptoms of Addison's disease and secondary adrenal insufficiency are similar. But, with Addison's disease, a person is more likely to experience hyperpigmentation (darkening of the skin), low blood pressure, and severe dehydration. These are uncommon with secondary adrenal insufficiency.

Adrenal insufficiency can sometimes become severe and lead to a potentially life-threatening condition known as an adrenal crisis. Symptoms include rapid heart rate, rapid breathing, abdominal or flank pain, dizziness, weakness, profuse sweating, high fever, nausea, vomiting, confusion, and unconsciousness.

An adrenal crisis is a medical emergency that can lead to coma and death if not treated immediately.


The treatment of adrenal hypersecretion and adrenal insufficiency varies by the underlying cause. The treatment may involve lifestyle changes, medications, and, in some cases, surgery.

Hormonal disorders are commonly treated by an endocrinologist, a physician who specializes in disorders of the endocrine system.

Cushing Syndrome

The treatment of Cushing syndrome may involve gradually tapering down the dose of steroids in people treated with drugs like prednisone.

If the cause is a pituitary tumor, your healthcare provider will likely recommend surgical removal of the pituitary gland, which can cure the condition in 90% of cases.

Adrenal Gland Tumors

It is recommended that most tumors, regardless of size, be surgically removed. Some healthcare providers will take a watch-and-wait approach and only consider surgery when the tumor approaches 5 centimeters (2 inches) in size.

Obstructive Sleep Apnea

The first-line treatment commonly includes a device called continuous positive airway pressure (CPAP), which blows air into the airways to keep them open at night.

Treatment of obstructive sleep apnea includes weight loss. According to Harvard Medical School, even losing 10% of body weight can have a big effect on sleep apnea.

Addison's Disease

Addison's disease is typically treated with hormone replacement therapy. Options include Cortef (hydrocortisone), prednisone, or methylprednisolone tablets to replace cortisol or Florinef (fludrocortisone acetate) to replace aldosterone.

An increased intake of salt (sodium) may also be required, particularly during exercise or when you have gastrointestinal problems like diarrhea.


Chronic stress can wreak havoc on a person's health and well-being. Regularly engaging in stress reduction strategies can help you better control stress and potentially lower your risk of heart disease.

This includes routine exercise, which not only improves your cardiovascular health but can improve your moods due to the release of "feel-good" hormones called endorphins.

Popular stress-reduction strategies include:

  • Yoga
  • Tai chi
  • Deep breathing exercises
  • Meditation
  • Guided imagery
  • Progressive muscle relaxation (PMR)
  • Biofeedback


Adrenaline is a hormone also known as epinephrine that is released by the adrenal glands as part of the “fight or flight” response. When faced with a threat or stress, the hormone stimulates the nervous system to rapidly respond to the crisis.

Although adrenaline is produced as a normal response to any threat, perceived or real, it can cause serious health problems if the hormone is persistently elevated or deficient. There are medical conditions (like Cushing's syndrome and Addison's disease) that can cause the overproduction and underproduction of adrenaline respectively. The treatment can vary by the diagnosed cause.

A Word From Verywell

If you have symptoms of Cushing syndrome or Addison's disease, it is important to see a healthcare provider who can order tests to confirm your suspicions. If you are experiencing insomnia, jitteriness, heart palpitations, and other stress-related symptoms, you should also speak with an expert who can offer tips on how to better manage your stress.

If self-help strategies fail to provide relief, do not hesitate to ask your healthcare provider for a referral to a therapist or psychiatrist who can provide one-on-one or group counseling to better target and address the causes of your stress. For extreme cases, medications can be prescribed.

13 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Michelle Pugle
Michelle Pugle, BA, MA, is an expert health writer with nearly a decade of contributing accurate and accessible health news and information to authority websites and print magazines. Her work focuses on lifestyle management, chronic illness, and mental health. Michelle is the author of Ana, Mia & Me: A Memoir From an Anorexic Teen Mind.