What is Cortisol?

Cortisol is a steroid hormone produced in the adrenal cortex of the adrenal glands that has many functions, including the metabolism of fats and sugars and the management of stress.

Cortisol secretion is dependent on the release of the hormone adrenocorticotropic hormone (ACTH) from the pituitary gland as well.

Pregnancy, stress, physical injury, or infection can affect cortisol levels, which vary throughout the day, being highest in the morning and lowest later in the day.

A blood, urine, or saliva test may be ordered to test cortisol levels. Most cortisol binds to proteins, with only a small amount considered biologically active, known as free plasma cortisol levels.

While a blood test measures both protein-bound cortisol and free cortisol, a saliva or urine test only tests free cortisol levels. The hypothalamic-pituitary-adrenal axis plays a crucial role in regulating cortisol levels.

Certain conditions, such as secondary adrenal insufficiency, can impact cortisol secretion. Moreover, cortisol is metabolized into various cortisol metabolites, which can be detected and quantified in tests.

A physician may advise the patient to refrain from strenuous activity the day preceding cortisol testing and specify rest 30 minutes prior to the test. Certain medications, such as amphetamines, steroids, estrogen, or oral contraceptives, can alter test results.

Cortisol Test: Why is it used?

Cortisol testing may be ordered if a physician suspects certain disorders such as Cushing's syndrome. This is sometimes found in individuals with high levels of cortisol. Symptoms suggestive of Cushing Syndrome may include:

• Elevated blood pressure
• High blood sugar
• Obesity, with weight distributed around the trunk
• Weak muscles
• Purple streaking around the abdomen
• Osteoporosis
• Skin that's easily broken

Cortisol levels may be examined in women with irregular menstrual periods and the presence of facial hair, and in children slow to develop and short in stature.

Testing may also be done when either adrenal insufficiency is suspected or a condition known as Addison's disease. In cases such as these, cortisol levels are too low, and individuals may experience:

• Loss of weight
• Weakness in muscles
• Fatigue
• Lowered blood pressure
• Pain in the abdomen
• Patches of darkened skin (Addison's disease)

A decrease in cortisol production, in addition to a stressful event or crisis, could trigger a life-threatening adrenal event requiring emergency medical attention. Symptoms of such an event may include:

• Severe pain in the legs, abdomen, or lower back that is sudden
• Vomiting and diarrhea, that results in dehydration
• Drop in blood pressure
• Loss of consciousness

A cortisol test may involve measuring blood cortisol levels through a cortisol blood test, which measures the cortisol level in a blood sample.

Salivary cortisol tests are also used to measure salivary cortisol levels, providing a non-invasive method to assess the function of the pituitary and adrenal glands.

Both blood and salivary cortisol tests are essential in diagnosing conditions of too much cortisol or decreased cortisol production.

Cortisol Test: How does it work?

The cortisol hormone rises and falls in what's known as a “diurnal variation” pattern. Levels are highest in the early morning hours and decline throughout the day. By midnight, cortisol levels are at their lowest.

While the hormone is produced in the adrenal glands, it is regulated by the hypothalamus in the brain and the pituitary gland. The timing of the cortisol test is critical since hormone levels vary widely throughout the day. A cortisol blood test measures the level of cortisol in the blood, providing important insights into adrenal function.

A test may be ordered late in the day if overproduction of cortisol is suspected. An early morning test may be administered if there is a likelihood of too little hormone production. Specific tests for cortisol may be used to diagnose different conditions, such as the 24-hour urine test for Cushing's syndrome or the ACTH stimulation test for Addison's disease. Other tests to determine proper pituitary or adrenal gland function include the ACTH stimulation test and the dexamethasone suppression test.

Measuring salivary cortisol is another method that can be used to assess cortisol levels non-invasively. This method is useful for evaluating diurnal variation and diagnosing conditions like Cushing's syndrome.

Cortisol Test: Test Results

Reference ranges may vary from lab to lab, and are as follows:

Normal Cortisol Levels

Adult/child

• Morning 5-23 micrograms per deciliter (mcg/dL) or 138-635 nanomoles per liter (nmol/L)
• Afternoon 3-16 mcg/dL or 83-441 nmol/L

High Cortisol Levels

Adult/child

• High levels of cortisol could indicate Cushing's syndrome, certain cancers, liver or kidney disease, depression, hyperthyroidism, obesity, pregnancy, or sepsis.

Low Cortisol Levels

Adult/child

• Low cortisol levels may signify Addison's disease, adrenal gland infection, pituitary gland cancer, or head injury. If initial findings are abnormal, suppression or stimulation testing may be ordered.

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