Norepinephrine vs. Epinephrine: What’s the Difference?

Epinephrine and norepinephrine belong to a group of naturally occurring compounds in the human body called catecholamines. They function as both hormones and neurotransmitters.

Hormones and neurotransmitters are both chemical messengers; however, hormones are secreted into the bloodstream and carry messages to the body’s tissues and organs through blood circulation. Neurotransmitters, on the other hand, are released into the space between nerve cells and deliver messages across nerve endings from one neighboring cell to another.

This article will explain some similarities and differences between epinephrine and norepinephrine. We will also talk about their medical uses.

Are epinephrine and norepinephrine the same as adrenaline?

Epinephrine is also called adrenaline. Norepinephrine is often referred to as noradrenaline. Both are natural chemicals made by the adrenal glands in the body. The adrenal glands are hat-shaped glands located above the kidneys.

The adrenal glands, specifically the adrenal cortex, also make other hormones such as cortisol (called the stress hormone). The pituitary gland in the brain controls the production of adrenal hormones.

What is the main difference between epinephrine and norepinephrine?

Epinephrine and norepinephrine are very similar chemical messengers with similar chemical structures. Both regulate the body’s sympathetic nervous system, which regulates the “fight or flight response” in a stressful situation.

As hormones, norepinephrine and epinephrine both affect the central nervous system and different body organs. They activate alpha and beta receptors in the brain and spinal cord. Having too much or too little epinephrine and norepinephrine can cause significant health problems.

While there are many similarities between them, there are also key differences in the effects of norepinephrine vs. epinephrine in the body. As mentioned, both epinephrine and norepinephrine affect alpha and beta receptors in the body. However, compared to norepinephrine, epinephrine has a more significant effect on the beta receptors, which are found in the heart, lungs, and blood vessels of skeletal muscles. Alpha receptors are only located in the arteries.

What is the function of epinephrine?

The function of epinephrine is to help the body mount a stress response. When the brain perceives danger, it activates the autonomic nervous system. The autonomic nervous system is a part of the nervous system that regulates the body’s involuntary actions like blood pressure, heart rate, respiration, digestion, and sexual arousal. When the autonomic nervous system is activated in threatening situations, it stimulates the adrenal gland to increase the release of epinephrine into the bloodstream. This is often called an adrenaline rush or “fight or flight response.”

Epinephrine activates alpha and beta receptors in almost all body tissues, including the heart, lungs, muscles, and blood vessels. As a result, epinephrine is responsible for redirecting blood flow to the heart and lungs, increasing heart rate, widening the breathing tubes for better breathing, and raising blood sugar levels. Overall, these effects will give you more energy, raise your focus and strength, and improve your overall physical performance so you can deal with the emerging threat or danger.

What is the function of norepinephrine?

The adrenal medulla produces the hormone norepinephrine in response to low blood pressure. Norepinephrine activates mostly the alpha receptors in arteries; it does exert its effects on beta receptors, though it is a lot less significant. Stimulating the alpha receptors leads to vasoconstriction (narrowing of the blood vessels), which raises the arterial blood pressure. Along with epinephrine, norepinephrine initiates responses to improve your survival during a fight-or-flight situation.

When do you use norepinephrine vs. epinephrine?

Epinephrine Uses

Doctors use epinephrine to treat severe and potentially life-threatening allergic reactions and health conditions, such as:

Anaphylactic shock. This is a severe and life-threatening allergic reaction that can interfere with breathing. It can occur due to an allergic reaction to foods, drug reactions, or bee stings. An epinephrine injection can be life-saving in anaphylaxis. It works by increasing the heart rate and blood pressure, improving blood flow while relaxing the muscles in the throat and airways, making breathing easier. Some people at high risk of anaphylaxis may be asked to carry an epinephrine auto-injector, such as an EpiPen, with them at all times.
Severe asthma attacks. Doctors may give epinephrine in nebulized or other inhaled form to prevent or treat severe asthma attacks.
Septic shock caused by severe infections. Epinephrine can be administered intravenously to correct very low blood pressure due to low levels of catecholamines.
Cardiac arrest. Epinephrine increases blood pressure and blood flow to vital organs like the heart and brain.

Norepinephrine Uses

Doctors use norepinephrine to increase systolic blood pressure in people with very low blood pressure. Norepinephrine may be used in the following situations:

Critical hypotension. This is the medical term for dangerously low blood pressure. It can occur after a heart attack, for example, when a weak and damaged heart muscle cannot pump blood effectively. Norepinephrine can help to maintain blood pressure in such patients.
Pericardial tamponade. This is a condition in which fluid in the membrane surrounding the heart (pericardium) makes it difficult for the heart to expand fully. Doctors remove the excess fluid using a needle and give norepinephrine as well.
Septic shock. This is a life-threatening condition in which the blood pressure drops to dangerously low levels during severe infection. Doctors use norepinephrine to raise blood pressure along with antibiotics to treat the infection.
Neurogenic shock. Extensive damage to nerve cells can lead to problems maintaining stable blood pressure, heart rate, and temperature. Doctors use norepinephrine in this situation to help regulate these vital parameters.

What happens if you have too little epinephrine or norepinephrine?

Norepinephrine is continuously released into the blood circulation to maintain blood pressure, while epinephrine is produced in response to stress. People with poor nutrition and chronic stress may have low levels of these hormones. Also, certain medications like methylphenidate (Ritalin) can make the body less sensitive to epinephrine and norepinephrine.

Low levels of epinephrine and norepinephrine can lead to various physical and mental health conditions, such as anxiety, depression, hypoglycemia (low blood sugar), fibromyalgia, migraines, sleep disorders, and restless legs syndrome.

What happens if you have too much epinephrine and norepinephrine?

Certain medical conditions can lead to an overproduction of epinephrine, norepinephrine, or both. This includes tumors of the adrenal glands such as pheochromocytoma or paraganglioma. Obesity and ongoing stress can also cause high levels of epinephrine and norepinephrine. Very rarely, medication dosing errors can lead to a norepinephrine or epinephrine overdose.

Too much epinephrine or norepinephrine in the body can lead to signs and symptoms such as anxiety, high blood pressure, heart palpitations, rapid heartbeat, weight loss, excessive sweating, and headaches.

When toy see a doctor?

Most people can naturally maintain adequate levels of a chemical messenger like epinephrine or norepinephrine by eating a healthy diet, exercising regularly, getting enough sleep, and practicing meditation or other such activities for stress relief. If you struggle with chronic stress, along with your primary care team, wellness professionals can help you learn to manage stress responses better.

However, if you have signs and symptoms that may indicate hormonal imbalance, you should see a doctor. Your primary care physician may refer you to an endocrinologist, a doctor who specializes in hormonal disorders. They can evaluate you and help find out if something is going on with your norepinephrine or epinephrine levels.

References:

https://www.health.harvard.edu/staying-healthy/understanding-the-stress-response