All About Cortisol

All About Cortisol

Anil Kumar, PhD
Jul 29 2020 07:30
Keywords: cortisol stress hormone, Cushing’s syndrome, Addisoson’s syndrome, diurnal cortisol


Cortisol is one of the stress hormones that adrenal glands produce.

It is a catabolic steroid hormone, meaning, it helps in metabolism by breaking down muscles, bones and builds fat.

Levels peak in the morning—when it helps us start with daily chores—then levels drop throughout the day. In that way, it works as adrenaline.

Any stress will build cortisol levels to fight off the stress stimulants. Those with a lifestyle of high stress will have high cortisol levels as the body constantly tries to fight the stress.

This results in fat accumulation—especially around waist—and weaker muscles and bones. On the other hand, deficiency results in fatigue, sluggishness, and no desire to exercise.

Cortisol has a characteristics 24-hour circadian rhythm which peaks after about 15-30 minutes of waking.

Using four saliva samples—in morning, noon, evening, and night—is a standard method to understand the diurnal rhythm of stress hormone drop.

A flat trend is strong indicator of Cushing’s syndrome, and problems with adrenal or pituitary glands.

Extremely low levels are due to Addison’s syndrome—a condition in which adrenal glands cannot produce enough cortisol (e.g., due to an autoimmune disease).

Controlling stress, regularly exercising, meditation, and eating healthy can help maintain healthy stress hormone levels.

What is cortisol?

The adrenal glands on top of kidneys release the stress hormone hydrocortisone, also known as cortisol. It is one of the glucose metabolizing hormones (thus the name glucocorticoids). Because almost all cells in the body have a cortisol receptor it is crucial for lot of different functions in the body. But as a catabolic steroid hormone, its most important role is in metabolism, by breaking down muscles, bones and building fat. It helps regulate blood pressure, blood sugar levels, salt and water balance. It also assists in reducing inflammation, and memory formation. During pregnancy, cortisol supports fetus development. There is a strong link between stress hormone and mood which makes it an important hormone for overall health and well-being.

Corticosterone is a similar hormone, but only in birds, reptiles, and rodents.



    Vitamin D and CVD – role of Vitamin D in heart health

    Thyroid and You – how thyroid impacts each of us

    All About Cortisol– summary of research on the stress hormone

    CRP and Heart Risk – read about a marker for low inflammation associated with heart attack

How do cortisol levels vary?

Cortisol levels have a well defined pattern. They are highest in the morning within 30 minutes of waking up when we are most energetic. The levels then drop throughout the day and reach lowest around 3 am before rising again. Night shift workers will have a different pattern and peak levels in the night—as the levels depend on daily routine.

Three different organs control the release of stress hormone in our body. The so called HPA-axis includes hypothalamus in the brain, the pituitary gland, and the adrenal gland. When cortisol levels are low, the hypothalamus releases CRH (corticotrophin-releasing hormone) which causes the pituitary gland to release another hormone called ACTH (adrenocorticotropic hormone). The adrenal glands will detect the ACTH levels and will release stress hormone. The hypothalamus will detect the cortisol levels and a feedback loop will be established by the controlled released of CRH.

Cortisol in some way works like adrenaline. During times of stress, it is released to fight the stress. This results in increasing heart rate, breathing, blood pressure, blood sugar, and muscle tension. During short term stress, it will shut down digestion and reproduction to fight off the stress stimulant. Thus, short bouts help cope with the daily stress in life, however, chronically high levels accelerate metabolism resulting in fat accumulation and weight gain. On the other hand, deficiency slows down metabolism causing fatigue, sluggishness, weight loss, and no desire for physical work.

Cortisol hormone trend during the day:


What are the effects of high cortisol levels?

Short bouts of high cortisol are good for the body as it helps fight off the stress stimulants. However, chronically high levels have undesired consequences and the symptoms include:

  • Weight gain – high levels cause fat build up in the belly, chest, and face – giving a apple-like shape.
  • Increased appetite – cortisol stimulates hunger center in the brain.
  • Tissue breakdown – as a catabolic hormone, it breaks down muscles resulting in less muscles and slow metabolism. That makes us feel weak and tired. It also breaks down other tissues such as bone and skin resulting in osteoporosis in bones and easy bruising, stretch marks, and thinning of skin.
  • Immune suppression – stress hormone keeps our immune system in check by interacting with white blood cells and its anti-inflammatory properties. Excess levels will suppress the immune system and make us feel sick.
  • Stomach upset and ulcers – excess stress hormone cranks up stomach acid production resulting in upset stomach and potentially dangerous ulcers. People with lot of stress tend to have stomach ulcers due to high cortisol levels.
  • Bloating and fluid retention – it stimulates the hormone responsible for minerals and salt control in the body. In this role, it can cause salt retention and water, resulting in bloating. It also makes the blood potassium drop which can impede insulin function resulting in diabetes.
  • Changes in libido and menstrual cycles are also associated with high levels of cortisol.
  • Increased thirst and frequent urination due to high appetite are potential symptoms of excess cortisol levels.

Cushing syndrome

A syndrome caused by pituitary tumors. Although rare—affecting about one-in-1,000 people—women are at four times higher risk. Cushing has most of the conditions associated with excess cortisol. Individuals with the syndrome will show weight gain in a very short period in mid-section, chest, abdomen, and face in contrast with thin legs and arms. Other symptoms include osteoporosis, high blood pressure, flushed and round face, mood swings, and changes in the skin (bruises and stretch marks).

What are the causes and effects of low cortisol levels?

  • Addison disease: the rare primary adrenal insufficiency disorder called Addison disease is caused by an autoimmune disease of adrenal glands.
  • Symptoms include fatigue, muscle loss, mood swings, and darkening of skin in different regions.
  • Dizziness when standing, weight loss, salt craving, low blood pressure have known associations with Addison disease.
  • Adrenal fatigue is a term applied to adrenal insufficiency and the symptoms closely relate to Addison’s disease.

How to test for cortisol levels?

Since stress hormone has a well defined 24 hour circadian pattern, a 4-point cortisol test is one of the most popular test. Four samples are collected throughout the day: morning, afternoon, evening, and night to understand the diurnal rhythm. For a basic understanding of your levels, an AM-PM test with one sample at the peak in morning and one in evening (or night) can be used. Tests can use saliva, urine, or blood samples.

Salivary cortisol testing is one of the most popular methods. Checking cortisol levels using a salivary elisa assay kit is an accurate and reliable method. It offers several advantages over a blood test:

  • Stress-free sample collection as often as necessary.
  • No lab or medical personnel required for sample collection
  • Saliva test measures free cortisol avoiding any aberrations in results from binding proteins
  • Lower cost due to the above reasons
  • Avoids false positives from medication. The fraction of the unbound free cortisol remains unchanged during medication, e.g., in women taking oral contraceptives

The biggest hurdle to accuracy of salivary testing is the compliance with saliva sampling. In a controlled study collecting 6 samples over 24 hours, 25% of participants missed collecting their samples within a given window. A well communicated procedure can help avoid such problems.

What factors affect cortisol levels?

The rise in stress hormone levels from stress starts at very early age. Newborns and infants show elevation from stress. In infants, inoculation, brief separation from mothers, heel stick – all elevate stress hormone levels. Other factors determining stress impact on cortisol:

  • Genetic difference: Studies on identical twins showed similar cortisol response before and after psychological stress which suggests our responses are genetically programmed. However, physical exercise didn’t show same behavior. This suggests our health levels and the extent of psychological stress have very different response, outside of genetic programming.
  • Sex difference: Males release 1.5-2 times more cortisol on exposure to psychological stress. In controlled studies, although levels didn’t rise as high, women showed larger decrease than men when they got short term social support from their partners.
  • Smoking: nicotine affects the HPA axis resulting in chronically elevated ACTH and cortisol levels. Smoking raises stress hormone levels all day long. This can be problematic since smokers respond less to any psychological stress to increase their levels to fight the stress stimulus.
  • Physical exercise: cortisol levels start to rise during strenuous exercise, e.g., running marathon. The levels peak 20-30 minutes after completion. However, low or moderate exercise may not show any rise. The effect of relaxation and meditation on reducing it is not yet fully understood.

How to lower cortisol levels to regain health?

  • Cutting down on stress – eating food is one of the most common ways of coping with stress but it builds up weight and the excess cortisol from stress trigger creates more fat, slows down metabolism, and breaks down muscles.
  • Eating small, frequent meals – they prevent insulin surge and control hunger and cravings.
  • Cutting down on salt – salt causes bloating and high BP; it makes the body retain water and deprives the bones of calcium.
  • Reducing alcohol consumption – excess alcohol makes the adrenal glands overreact.
  • Quit smoking – nicotine affects the body’s ability to raise cortisol levels in response to any psychological stress to fight the stress stimulus
  • Taking caffeine in moderation – as caffeine raises the cortisol levels

How to lower stress levels?

  • Physical activity – It is the best solution to lower stress and cortisol levels as it builds muscles, reduces fat in body and improves insulin resistance; physical activity also takes the focus away from stress and the cravings to eat more.
  • Controlling hunger and focusing on other things in order not to gain weight; avoiding ‘comfort foods’ that have lot of fat & carbohydrates giving high calories.
  • Improving self esteem and practicing positive self-talk so that psychological triggers are under control.
  • Meditation, Yoga, Thai-Chi, and Chi-Gong are known to lower stress.
  • Massage helps work the muscles and lower stress.
  • Making time for yourself by organizing and simplifying; working on your priorities helps with lower unexpected triggers of stress.
  • Spending time with family and friends prevents emotional triggers and motivates us to follow our plans.
  • Being careful with what herbal and medication products you use.

For reference, please see:

  • ZRT lab’s excellent discussion and plots of diurnal cortisol curves for healthy individuals as well as patients with chronic stress, chronic fatigue, and burnout symptoms.
  • The intricate details of a saliva based cortisol testing for Cushing Syndrome from the experts at Mayo Clinic.
  • Cortisol vs pregnancy: The circadian rhythm of free cortisol in pregnant women starts to change around 20th week of pregnancy. Although the diurnal rhythm is maintained, the mean cortisol levels increase by 1.5-2 times with morning levels increasing several times higher than normal levels. Also, the peak levels lag behind approximately 90 minutes likely due to delayed activation of the HPA axis. The fact that external stimulation of CRH does not increase ACTH and salivary cortisol levels supports this observation. The levels return back to normal after 5-7 days of delivery. Original publication: Psychoneuroendocronology, Vol. 19, No. 4, 1999 (page 317).


For information purposes only—not to be used for diagnosis or to replace advice from a medical professional. You can order multiple saliva hormone testing kits: a basic At Home Cortisol Test (for morning and evening samples) or a comprehensive diurnal cortisol test for testing the 24 hour circadian rhythm. Information on other health tests can be found here See the full list of CLIA-certified at-home health test from for free shipping and physician-approved reports.