What is cortisol? 
HormonesMood and Mental Health

What is cortisol? 

Written by

Anna Roell
21 April, 2023

Medically checked article All HOMED-IQ content is reviewed by medical specialists

Stress is a normal body response that happens to everyone at some point. It is defined as a physical and mental state of tension caused by feeling pressure or threatened. The stress response evolved throughout history to prepare humans for potentially life-threatening situations. This prepares us to react quickly to danger and is also known as the “fight or flight” response (Harvard Health, 2020). While we are less often faced with life-threatening situations compared to the lives of our ancestors, situations like a work deadline, conflict with another person, or financial struggles can also trigger the stress response. 

The stress response is activated when we are exposed to stimuli which our brains perceive as dangerous (Mayo Clinic, 2021). This triggers a release of hormones that cause the physical changes associated with stress, such as sweating, increased heart rate, and muscle tension. The hormone cortisol plays the most important role in regulating the stress response, which is why it is also known as the “stress hormone”. While cortisol is necessary for our bodies to function, cortisol that is too high or too low can damage our health. Read on to learn more about the hormone cortisol, its function in the body, and reasons why it can be too high or too low. 

What is the function of cortisol? 

Cortisol is a hormone. Hormones are chemical messengers that regulate a variety of processes in our body. Cortisol is produced in the adrenal glands which are located on top of the kidneys. This hormone has many important roles in the body, such as regulating the body’s stress response, immune system, sleep-wake rhythm, metabolism, blood pressure, and blood sugar (Cleveland Clinic, 2021). 

Cortisol is broken down in the liver and excreted in the urine. The level of cortisol in the blood fluctuates naturally during the day, with levels usually being highest in the morning and lowest around midnight (UMRC, 2023). The body works to maintain consistent levels of cortisol in the body, also known as homeostasis. Cortisol levels are consistently too high or too low can have negative effects on health, and may be caused by a medical condition that needs treatment (Cleveland Clinic, 2021).

What does cortisol do during stress?

The goal of the stress response is to prepare our bodies to react quickly to danger. The two primary hormones released during the stress response are cortisol and adrenaline. These hormones can act rapidly on multiple body systems at once, causing a range of symptoms. Adrenaline makes the heart beat faster, increases blood flow to the brain and muscles, and raises blood pressure. Cortisol increases sugars in the bloodstream that can be easily used for energy, as well as boosts the availability of substances that repair body tissues (Mayo Clinic, 2021). During acute stress, cortisol also slows body functions that are non-essential in a fight-or-flight situation, such as the digestive system. High cortisol from the stress response is designed to be a temporary reaction. While high cortisol can help us during a life-threatening situation, long-term exposure to high levels can harm our health. 

Cortisol and Cushing’s syndrome

Hypercortisolism is a condition in which the body produces too much cortisol. This can be caused by medication use or by tumors on the adrenal gland, pituitary gland, or other parts of the body. Cushing’s syndrome is the collective name for the symptoms that occur due to hypercortisolism, regardless of the cause (Cleveland Clinic, 2022).

Causes of Cushing’s syndrome

Cushing’s syndrome most often occurs in people who take corticosteroid medications for long periods of time (NIH, 2018). As these medications are synthetic forms of cortisol, long-term exposure can cause symptoms of hypercortisolism. Corticosteroid medications are used treat a range of diseases, including rheumatoid arthritis, chronic asthma, COPD, or eczema (Mayo Clinic, 2022). They may be injected, taken as a pill, or used directly on the skin as a cream. 

Tumors within the body can also cause an overproduction of cortisol. A tumor on the adrenal gland can produce too much cortisol, while tumors on the pituitary gland or in other parts of the body (such as the chest) can produce ACTH, the hormone that tells the adrenal glands to make cortisol (Pluta et al., 2011). Most adrenal and ACTH-producing tumors are benign, or non cancerous. Cushing’s disease occurs when Cushing’s syndrome is caused by an ACTH-producing tumor. 

What are the symptoms of high cortisol?

The stress response is designed to occur only until the source of danger is gone. However, if real or perceived stressors are always present, the fight-or-flight response may remain constantly activated. The same is true if an individual takes medications that increase cortisol or has a medical condition in which too much cortisol is produced. As cortisol is a hormone that affects many body systems, too much cortisol can cause a variety of symptoms and negative health effects. Elevated cortisol from chronic stress, medication use, or other health problems can cause:

  • Weight gain: Cortisol builds fat reserves that the body can use in situations where it needs to provide extra energy. This can increase appetite, particularly for energy-dense (high calorie) foods. High levels of cortisol can also affect fat distribution on the body, with increased fat storage in the abdomen (chest, back, and belly) or face (Clutter, 2011).
  • Increased blood sugar: cortisol can elevate blood sugar levels to ensure that the body is appropriately energised to react to danger. However, long term high cortisol can lead to persistent high blood sugar levels (Cleveland Clinic, 2021).
  • Insulin resistance: since cortisol is designed to increase short-term energy availability, it reduces the secretion of insulin in the body and can make fat and muscle cells not respond as well to insulin, also known as insulin resistance (UCSF, 2023). In people with diabetes, this may mean you will need to take more insulin to control your blood sugar. 
  • High blood pressure: cortisol increases blood pressure and heart rate as a part of the stress response. Chronically elevated cortisol is associated with increased blood pressure and risk of cardiovascular events, such as stroke or heart attack (Inoue et al., 2021).
  • Loss of muscle strength and volume: persistently high cortisol can stop protein synthesis, meaning it is harder for your body to build muscle. It can also cause the body to use muscle as a source of energy, which is why high cortisol is associated with lowered muscle strength (Peeters at el., 2008).
  • Increased susceptibility to infection: during short-term stress, cortisol suppresses inflammation and the immune system while the body responds to danger. However, long-term high cortisol can cause increased inflammation and a weaker immune response (Morey et al., 2015). 
  • Anxiety and depression: increased cortisol has been linked with mental health conditions such as depression (Dziurkowska & Wesolowski, 2021) and anxiety (Mayo Clinic, 2021).
  • Skin changes: high cortisol can cause the breakdown of proteins in skin and weakening of blood vessels, leading to thinning skin that may bruise, become discoloured, break easily, or develop red-purple streaks (striae) (Philips, 2007).
  • Hair growth in women (hirsutism): women who have high cortisol due to overproduction of the hormone ACTH may experience dark and coarse hair growth where hair does not usually grow, such as the face and back (Hafsi & Badri, 2022). This is because ACTH also can stimulate the production of androgens, hormones responsible for certain male sex characteristics, such as facial hair.

What can you do if your cortisol level is too high?

The treatment for high cortisol depends on the cause. If high cortisol is caused by medication use, stopping corticosteroids and/or taking drugs that reduce cortisol may be recommended. If high cortisol is caused by a tumor, radiation, chemotherapy, or surgery may be used (Cleveland Clinic, 2022). If you are diagnosed with Cushing’s syndrome, your healthcare provider will work with you to identify the cause and an appropriate treatment plan.

If your cortisol levels are elevated from chronic stress or lifestyle factors, stress management can have a positive effect. Try the following tips:

  • Reduce your caffeine and alcohol intake 
  • Get enough sleep and follow a consistent sleep schedule
  • Exercise regularly, such as walking or swimming
  • Meditate or practice deep breathing
  • Follow a healthy diet 
  • Make time for activities that are fun and relaxing

Source: Harvard Health, 2021

Can you have low cortisol?

Cortisol is essential for good health, and both too much and too little can cause health problems. Low cortisol (or hypocortisolism) occurs when the adrenal glands do not produce enough cortisol. This is also known as adrenal insufficiency. There are three types of adrenal insufficiency:

  • Primary adrenal insufficiency is also caused Addison’s disease and occurs when the adrenal gland does not produce enough cortisol.
  • Secondary adrenal insufficiency occurs when the pituitary gland does not produce enough ACTH, the hormone that tells the adrenal glands to make cortisol.  
  • Tertiary adrenal insufficiency occurs when the hypothalamus in the brain does not produce enough CRH- the hormone that tells the pituitary gland to produce ACTH. 

Source: NIH, 2018

Causes of low cortisol

Low cortisol from adrenal insufficiency can be caused by:

  • Autoimmune diseases 
  • Infection of the adrenal glands
  • Genetic disorders that affect the development or function of the adrenal or pituitary gland
  • Surgical removal of the adrenal gland for other reasons
  • Suddenly stopping corticosteroids
  • Pituitary tumors or infection

Source: NIH, 2018

Symptoms of low cortisol

Symptoms of adrenal insufficiency include fatigue, general weakness, and weight loss. The severity and types of symptoms experience depend on the cause of the adrenal insufficiency and the severity of the lack of cortisol. Other symptoms can include:

  • Abdominal pain
  • Loss of appetite
  • Nausea and vomiting
  • Diarrhoea
  • Low blood pressure
  • Craving salty foods
  • Low blood pressure that drops when standing, causing dizziness or fainting
  • Decreased sexual desire

Source: NIH, 2018

What can you do if your cortisol level is too low?

Adrenal insufficiency is treated with hormone replacement therapy. Treatment is often required for life, usually with daily oral medication (Nieman, 2021). Correct use of replacement medications is needed to minimise symptoms and avoid adrenal crisis, a life-threatening condition caused by a severe lack of cortisol. With correct medical care, people with adrenal insufficiency can live active and healthy lives.


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About the author

Anna Roell

Anna is a trained nurse and health economist specializing in epidemiology, combining her medical and scientific interests. Her goal is to improve others' understanding of medical information and to communicate it in an understandable way. Anna is originally from Germany and now lives in Amsterdam. What she appreciates most about Amsterdam is the open-minded, active attitude of the people, the markets, and the beautiful nature in the areas surrounding Amsterdam.