55% of Americans report being stressed, and 50% report feeling fatigued. Stress and fatigue are connected by the hormone cortisol. This hormone plays a role in these feelings and symptoms and is involved in multiple other body functions.
This article will discuss cortisol, including its role in the body, symptoms of varying cortisol levels, how to test for it, and considerations for managing cortisol levels using a functional approach.
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What is Cortisol?
Cortisol is a hormone released by the adrenal glands. Its production and release are regulated by the Hypothalamic Pituitary Adrenal (HPA) axis, which is influenced by stress and the circadian rhythm, the body's sleep-wake cycle.
Cortisol can be converted into its inactive form, cortisone, in the kidneys and pancreas. The majority of circulating cortisol is in this inactive form. Most tissues can convert cortisone back into cortisol. The body adjusts the conversion based on need; more stress may lead to more conversion of cortisone to cortisol.
What is Cortisol's Role in The Body?
Cortisol receptors are found almost everywhere in the body. Cortisol can influence the following systems: respiratory, reproductive, immune, musculoskeletal, nervous, cardiovascular, integumentary, gastrointestinal, and more through its role in the stress response and the circadian rhythm.
Stress response
The body's nervous system has two main systems: the parasympathetic and the sympathetic. The parasympathetic system is responsible for resting and digesting, while the sympathetic system is the fight-or-flight response. The amygdala is a center in the brain responsible for producing fear. When a stressor occurs, the amygdala sets off a cascade in the brain that activates the fight or flight response. The amygdala signals the hypothalamus, another center in the brain, that will then signal the pituitary gland and ultimately lead to the release of the adrenaline hormones, norepinephrine and epinephrine. These hormones increase blood pressure, heart rate, and respiration. About 15 minutes later, the amygdala will then cause activation of the Hypothalamic Pituitary Adrenal (HPA) axis. The HPA axis leads to the production of cortisol, which may influence inflammatory, immune, metabolic, hormone, and gastrointestinal changes.
As we discuss these changes, it's important to remember the stress response's evolutionary purpose: survival. Because of this, these various mechanisms will cause the body to prioritize resources towards immediate survival needs. Let's assess these effects:
Metabolic Function
Cortisol increases glucose levels by increasing pathways that make glucose and inhibiting pathways that break it down. Glucose is the body's primary precursor to ATP, the body's energy source. Increasing glucose functions to fuel the brain and tissues of the body.
Although the exact mechanism is unclear, cortisol seems to influence blood pressure, potentially increasing it in high amounts and lowering it in low amounts. This may affect blood flow around the body, thus influencing the delivery of oxygen and nutrients to the tissues.
Immune and Inflammatory Response
Cortisol influences the immune response through various mechanisms, including affecting certain antibody production. It also may lead to apoptosis, or cell death, of certain inflammatory cells.
Hormone Production
Cortisol can influence gonadotropin-releasing hormone (GnRH), which controls the menstrual cycle in women, and testosterone and sperm production in men. Thus, menstrual irregularities, low sperm, and low testosterone can result. These symptoms are often associated with infertility. Reproduction is not a priority in a survival state.
Cortisol affects levels of ghrelin and leptin. Ghrelin is referred to as the "hunger hormone" as it induces hunger. Leptin, on the other hand, will cause satiety. Cortisol may lower leptin while increasing ghrelin, potentially leading to weight gain, especially in the abdominal area. Regarding survival, food is how we obtain and create energy in the body, which is essential for life.
Gastrointestinal (GI) System
Cortisol can slow food movement through the stomach, leading to bloating and indigestion. It can also increase transit time in the colon, leading to diarrhea. Cortisol can also cause increased sensitivities in the tissues of the esophagus, causing heartburn symptoms without the increase of stomach acid. Cortisol can also negatively impact the microbiome of the GI tract, affecting digestion, absorption, immune function, and more. Lastly, cortisol can affect the permeability of the small intestine, leading to altered digestion and absorption. Like reproduction, gastrointestinal function is not essential in an acute survival state.
Cortisol as a Circadian Rhythm Hormone
Cortisol also affects our circadian rhythm independent of its role in the stress response. Our body has a 24-hour sleep-wake cycle or circadian rhythm. During this rhythm, cortisol is released in a large amount in the morning, known as the Cortisol Awakening Response (CAR). Its levels will reduce throughout the day until night when levels are lowest. Because of this role, cortisol has been called our "daytime hormone."
However, even though cortisol's role in the circadian rhythm is independent of its role in the stress response, they can affect each other. The duration of stress exposure can cause both chronically high and low cortisol. This, in turn, can affect the cortisol release during the circadian rhythm and thus lead to fatigue, sleeplessness, and more.
What Happens if Cortisol is Too High?
Cushing syndrome is a condition of excess cortisol. Caused by either a tumor or overmedication with corticosteroids (cortisol-containing drugs), symptoms include weight gain in the face (called "moon face"), fatty deposits between the shoulder blades ("buffalo hump"), high blood pressure, muscle weakness and more.
When cortisol is high, but not due to Cushing syndrome, symptoms can be similar to those seen in Cushing syndrome but are not as severe and include:
- Impaired memory
- Weight gain
- Accelerated aging
- Increased risk of depression
- Round face
- Muscle weakness
- Easy bruising
What Happens if Cortisol is Low?
Addison's disease, also called primary adrenal insufficiency, occurs when the adrenal glands produce little to no cortisol. Addison's is primarily caused by an autoimmune reaction, although certain cancers, infections, or pituitary conditions can also be a cause.
Like the relationship discussed above between high cortisol symptoms and Cushing syndrome, low cortisol symptoms tend to mimic Addison's disease symptoms and include:
- Chronic fatigue
- Loss of appetite
- Stomach pain
How to Test Cortisol Levels
Cortisol levels can be tested in the blood, saliva, and urine.
Blood
Blood testing looks at hormones circulating in the bloodstream at that particular time. Blood testing can be useful to check for conditions such as Cushing syndrome and Addison's disease, as the cortisol levels will be grossly out of range in both syndromes, independent of time of day. However, cortisol blood testing may not be the best for assessing cortisol in relation to stress.
Hormones in the blood are bound to carrier molecules which make them inactive. Cortisol should be highest in the morning and trickle down throughout the day. But, this pattern is not always followed, especially in those with chronic stress. Timing of the test matters, and ideally cortisol levels would be checked numerous times to assess the entire cortisol curve, which can be hard to do with blood testing. Additionally, needles cause fear and apprehension for many people and can induce a stress response, possibly leading to inaccurate results.
Saliva
Salivary testing, like the Diurnal Cortisol Profile by Doctor's Data, can efficiently assess cortisol levels. Salivary testing shows the amount of free cortisol that is available for immediate use. Additionally, salivary cortisol is often checked throughout the day, allowing us to evaluate the entire cortisol curve. Saliva testing can also assess the CAR. Research has shown that the CAR can be directly linked to autoimmune, gastrointestinal diseases, depression, and blood sugar irregularities.
Urine
Urine testing can show hormone metabolites or breakdown products. This allows us to understand how the body breaks hormones down, which can be helpful when evaluating high and low levels. A 24-hour urine cortisol test is often ordered by a physician to aid in the diagnosis of Cushing and Addison's syndromes. However, the DUTCH Complete test, by Precision Analytical, is a urine test that assesses reproductive hormones and other stress-related hormones, including cortisol and cortisone and metabolites of the other fight or flight hormones, epinephrine and norepinephrine. This test gives a comprehensive view of the entire HPA axis.
How to Balance Cortisol Levels Naturally
Breathing exercises
Deep breathing exercises may help stimulate the parasympathetic system and thus can support the sympathetic system, including the release of cortisol. A meta-analysis including over 700 people suggested that breathwork could help manage stress levels.
Sleep
Sleep is important for numerous body functions, including cortisol production. Lack of sleep may lead to increased cortisol levels. Current recommendations indicate that seven or more hours of sleep for adults is ideal.
Healthy Relationships
Interactions with people can significantly influence stress levels and, thus, cortisol production. Laughing may promote the release of endorphins, or "happy" chemicals, which can help manage cortisol levels.
Adaptogenic Herbs
Adaptogens, as their name implies, may help the body adapt to stress. Rhodiola, Ashwagandha, Asian Ginseng, and Holy Basil are examples of adaptogens that may help to modulate cortisol levels.
Summary
Cortisol is an important hormone, playing a role in the stress response and the circadian rhythm. Because of these important roles in the body, cortisol levels can affect nearly every body system, including the gastrointestinal, reproductive, and central nervous systems. Thus, testing cortisol levels can give insight into the root cause of many symptoms, and a functional approach to management can help support balanced cortisol levels.
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