Norepinephrine

Your brain and spinal cord make up your CNS. This is your body's main processing hub, so to speak—where external and internal information gets interpreted. It controls a host of things, including your routine movements, bodily functions, senses, thoughts, hunger levels, and more.

The CNS is able to communicate with your body because of nerve cells called neurons. You have around 86 billion of them, and their job is to transmit signals from your brain to your muscles and cells—why they are also called chemical messengers or neurotransmitters.2

Specialized neurons located within your brainstem and spinal cord, called postganglionic neurons, are among them. These are the neurons that release norepinephrine.

Once released, NE travels to its target nerve, binds to the nerve's receptor, and directs it take an action.3 That directive might be go to sleep or wake up, be more focused, feel happy, and much more.

Norepinephrine is also produced in the inner part of your adrenal glands called the adrenal medulla. In this case, NE is generated because of the sympathetic nervous system (SNS)—the driving force behind your fight-or-flight response.

When the body senses stress, your SNS signals your adrenal glands to release norepinephrine. NE then travels through your bloodstream and, as a hormone, initiates a stress response that allows you to quickly mobilize your body and brain so you can protect yourself.

Norepinephrine is at the center of a variety of functions that help keep you healthy. Sometimes, you may be well aware that it's coursing through your veins; think of sweaty palms when you're nervous or a racing heartbeat when you're scared. Other times, you may have no idea it's even there.

Keeps Your Biorhythms Steady

Biorhythms are body cycles involved in your physical, emotional, and intellectual health. Low amounts of norepinephrine are always circulating in your system to keep these cycles stable.

1. Blood flow to your skeletal muscles
2. Skeletal muscle contraction, which enables you to move
3. Glucose levels in your bloodstream
4. Mood stabilit

All together, NE affects numerous organs throughout your body, including:6

Eyes: NE increases tear production and dilates the pupils in response to light and emotion.

Kidneys: NE triggers your kidneys to release renin, which regulates salt and water balance.

Pancreas: NE triggers your pancreas to release glucagon so that your liver can produce more glucose.

Lymphoid organs: NE stimulates such organs as your spleen, thymus, and lymph nodes to help your immune system fight infection.

Intestines: NE decreases blood flow to your intestines and slows down your digestive system.

Norepinephrine enables your stress response to protect you from danger, whether actual or perceived.

Take being exposed to extreme cold, for example. Your body knows that most of its heat is lost through your skin. To keep you well, you need to conserve whatever warmth you have.

To do that, your nerves release norepinephrine, which then binds to cell receptors in your skin. Because NE narrows blood vessels, it reduces blood flow to the skin, making heat less able to escape.

Other types of threats trigger a different response. When your brain perceives an external threat like someone chasing you, for example, part of the brain known as the hypothalamus excites your SNS. This triggers your adrenal glands to pump norepinephrine.

As part of this response, norepinephrine increases:

• Alertness
• Focus
• Pain tolerance
• Reaction time
• Breathing rate
• Memory retrieval

Digestion and the immune system are treated as non-essential functions during this period. NE shuts them down so that more energy can go to the functions needed to keep you safe.

Together with adrenaline, norepinephrine also raises your heart rate and blood pressure, and stimulates your liver to produce more blood sugar (glucose) so that your body can use it for energy.

A similar reaction can occur in situations that simply make you feel nervous or stressed, but that aren't true threats (e.g., a tense work meeting or an argument with a partner).

Low amounts of norepinephrine continuously move through your central nervous system to regulate your basic bodily functions. When faced with stress or danger, your hypothalamus alerts your brain to pump out more norepinephrine to gear you up for action.

Healthcare providers don't typically test norepinephrine levels during routine check-ups. They may suspect a change in your NE levels based on your symptoms, though, in which case they may order a urine or blood test to investigate.

The normal norepinephrine range for a blood test is between 70 and 1700 picograms per millilitre (pg/mL). There are numerous explanations for why your NE levels could be higher or lower than that, from rare tumors to anxiety and stress.

The cause of the change in your NE levels may not be immediately clear to your healthcare provider. In that case, they will need to investigate further by performing more tests based on your symptoms.

Low norepinephrine levels are a hallmark of several major conditions, including:

• Major depressive disorder
• The depression phase of bipolar disorder
• Other mood disorders
• Fibromyalgia
• Chronic fatigue syndrome
• Attention deficit disorders
• Low blood pressure (hypotension)

Each of these conditions has its own distinct profile of symptoms. That said, they also have several symptoms in common, many of which point to low norepinephrine.

These include:

• Loss of alertness
• Memory problems
• Depression
• Lack of arousal and interest
• Brain fog
• Fatigue
• Lack of motivation

A somewhat high NE activity level makes you happy, and a really high level makes you euphoric. Many recreational drugs get people "high" by increasing levels of norepinephrine and another neurotransmitter, dopamine.8

Conditions associated with having elevated NE levels include:

• Anxiety disorders
• Pheochromocytoma, a tumor on the adrenal glands9
• Chronic stress
• The manic phase of bipolar disorder

Like conditions related to low norepinephrine, those related to high NE have both unique and shared symptoms as well.

Symptoms that overlap and point to high norepinephrine levels include:

• Worry, anxiety, racing thoughts
• Irritability
• Insomnia
• Fear of crowds
• Claustrophobia
• Restless sleep
• Muscle tension or cramps
• Impaired concentration

Paroxysmal sympathetic hyperactivity (PSH) is a term that describes a group of symptoms related to being "stuck" in fight-or-flight mode—a possible outcome of too-high norepinephrine.

One of the most common causes of PSH is traumatic brain injury, but it has also been linked to stroke, spinal cord injury, and inflammation in the brain (encephalitis).

Symptoms of paroxysmal sympathetic hyperactivity include:

• Rapid heartbeat
• High blood pressure
• Heart palpitations
• Sweating
• Anxiety
• Headache
• Pale skin
• Low blood sugar
• Weight loss

Recap

Having too much or too little NE can cause symptoms that are common across many health conditions. If you are experiencing mood swings, anxiety, headaches, fatigue, or other NE-related symptoms, your healthcare provider may order a urine or blood test to measure your norepinephrine levels.