A stress hormone produced by the adrenal glands with extensive effects on various organs in the body. It has anti-inflammatory properties, maintains blood glucose levels, blood pressure, and muscle strength, and helps balance salt and fluid levels. When the body is subjected to stress, cortisol production is increased. If stress is prolonged, this can lead to so-called adrenal fatigue and eventually burnout, where the adrenal glands are no longer able to produce sufficient cortisol. Because the body, from an evolutionary perspective, prioritizes the production of cortisol ("fight-or-flight hormone"), this comes at the expense of the production of other hormones such as DHEA, progesterone, estrogen, and testosterone.
Hormones
Cortisol
Free cortisol in saliva; measured late in the evening, a test when too much cortisol is suspected.
Everything about this testWhat it measures
Cortisol is made by the adrenal glands, controlled by ACTH from the pituitary gland. Saliva contains the free, active part of cortisol, which is not bound to proteins in the blood. Cortisol has a strong daily rhythm: high shortly after waking up and low around midnight. With saliva, it can be measured without a needle at a fixed time, for example late in the evening or at several moments across the day (a daily profile).
- Cushing's syndrome (too much cortisol): a raised value in saliva around midnight is one of the standard tests for this
- Suppression of the body's own cortisol production by corticosteroids, although a morning cortisol measurement in the blood is more usual for this
High
A raised value is often due to the way the sample was collected: brushing your teeth, eating, drinking or smoking shortly beforehand, bleeding gums, or hydrocortisone cream on the hands or around the mouth. Tension, lack of sleep, night shifts, jet lag, illness, heavy exercise and alcohol also raise the value; in the morning, the value is supposed to be high. A repeatedly raised value around midnight may fit Cushing's syndrome, with symptoms such as weight gain around the trunk with thin arms and legs, a round and red face, thin skin with bruises, muscle weakness, high blood pressure and high blood sugar. Overweight, depression and a lot of alcohol can also give a raised cortisol without Cushing's; that is why the hospital repeats the measurements at several moments.
Low
A low value around midnight is normal. A low value in the morning is usually because the sample was collected later than shortly after waking up, or due to use of corticosteroids (tablets, inhaler, nasal spray, skin cream or injection), which suppress the body's own production. A true deficiency due to a disease of the adrenal glands or the pituitary gland is rare and goes with symptoms such as severe tiredness, weight loss, low blood pressure, nausea and salt craving; it is diagnosed with a blood test, not with saliva. A low or 'flat' daily profile is no proof of 'adrenal fatigue': that is not a recognized condition.
Preparation
- Fill the first tube straight after waking up and the next ones after 30 and 60 minutes. For the day profile, further tubes follow 2, 5, 8 and 12 hours after waking up, each at least 30 minutes after eating or drinking. Choose a normal day and get up at your usual time.
- Do not eat, drink, smoke or brush your teeth until after the third tube. Do not use mouthwash or dental floss that day.
- Do you use hormone preparations such as hydrocortisone or progesterone? Then stop 48 hours beforehand, in consultation with your doctor.
If your result is abnormal
With a raised value around midnight and matching symptoms, the measurement is repeated, usually together with a dexamethasone suppression test or cortisol in 24-hour urine, and if an abnormality is confirmed, referral to an internist-endocrinologist follows. With symptoms that fit a cortisol deficiency, a cortisol measurement in the blood early in the morning follows and, if needed, measurement of ACTH. With an abnormal daily profile without such symptoms, there is usually no further hormone testing.
Reliability
Cortisol in saliva around midnight is one of the standard tests for detecting too much cortisol, alongside the dexamethasone suppression test and cortisol in 24-hour urine; the hospital repeats these measurements at different moments because Cushing's syndrome is difficult to prove. Outside that question, the meaning of saliva cortisol is not well supported. A daily profile to measure stress, burnout or 'adrenal fatigue' is not supported by evidence: adrenal fatigue is not recognized in mainstream medicine and there is no validated test for it. The symptoms people experience are real, but often have another cause, such as an underactive thyroid, sleep apnea or depression.
Limitations
- Collection: do not eat, drink, smoke or brush your teeth just before collecting; brushing your teeth can strongly distort the result. Rinse your mouth with water about ten minutes beforehand.
- Timing: only a sample taken at the agreed time can be compared with the reference values; with night shifts, jet lag or an irregular sleep pattern, the daily rhythm is shifted.
- Corticosteroids in any form lower the body's own production; hydrocortisone on the skin or in the mouth can contaminate the sample and give a falsely high result.
- Tension, illness, heavy exercise, alcohol and lack of sleep temporarily raise the value. Reference values differ between laboratories and measurement methods.
How common is this
Cushing's syndrome due to a tumor of the pituitary or adrenal gland is rare: in the Netherlands, about 50 people per year are given this diagnosis, and the Netherlands has an estimated 150 to 200 people with this condition. The most common cause of too much cortisol is the use of corticosteroids such as prednisone or dexamethasone. Tiredness and stress symptoms are much more common and usually do not fit an adrenal disease.
Who is this useful for
Useful with symptoms that fit too much cortisol, such as weight gain around the trunk with thin arms and legs, a round and red face, thin skin with bruises and muscle weakness, with a sample late in the evening and in consultation with a doctor. Not useful for measuring stress, burnout, tiredness or 'adrenal fatigue', or for choosing a treatment or supplement based on it: a daily profile is not supported by evidence for this, and in healthy people under a lot of tension, the result cannot be interpreted.
Downsides and risks
- An abnormal daily profile can wrongly be seen as proof of adrenal fatigue or chronic stress and lead to expensive supplements or hormone products; some of these contain steroids and can harm your health.
- A falsely raised value due to incorrect collection can cause unnecessary worry about Cushing's syndrome and unnecessary follow-up tests.
Sources
Always discuss an abnormal result with your GP. If a result is strongly abnormal, we try to reach you as soon as possible. Read your result yourself as well and contact your GP if in doubt. A test does not make a diagnosis. Read more about risks and results