Cortisol Test

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Also known as: Serum Cortisol, Urine Cortisol, Urinary Free Cortisol, Salivary Cortisol
Formal name: Cortisol
Related tests: ACTH, Aldosterone, Synacthen stimulation test, Dexamethasone Suppression Test

The Test Sample

What is being tested?

Cortisol is a steroid hormone, produced by the adrenal gland, which is essential for survival. Production and secretion of cortisol is stimulated by ACTH (adrenocorticotropic hormone), a hormone produced by the pituitary gland – a tiny organ located inside the head below the brain. The concentration of cortisol in the blood increases during times of stress, and it also helps regulate the immune system. Heat, cold, infection, trauma, exercise, obesity, and debilitating disease influence cortisol secretion. The hormone is secreted in a daily pattern, rising in the early morning, peaking around 8 a.m., and declining in the evening. This pattern, a “diurnal variation” or “circadian rhythm,” can change in long term night shift workers.

Inadequate concentrations of cortisol within the blood can cause nonspecific symptoms such as weight loss, muscle weakness, fatigue, low blood pressure or abdominal pain and exposure to stress can cause an adrenal crisis that requires immediate medical attention. 

Decreased cortisol production may be seen with:

  • An underactive pituitary gland or a pituitary gland tumour that inhibits ACTH production. This is known as secondary adrenal insufficiency.
  • Underactive or damaged adrenal glands (adrenal insufficiency) that limit cortisol production. This is referred to as primary adrenal insufficiency and is also known as Addison’s disease.
  • Too much cortisol within the bloodstream can cause increased blood pressure, high blood sugar (glucose) concentrations, obesity, fragile skin, purple streaks on the tummy, muscle weakness, and osteoporosis. Women may have irregular menstrual periods and increased hair on the face; children may have delayed development and a short stature.

    Increased cortisol production may be seen with:

  • ACTH-producing tumours, in the pituitary gland and/or in other parts of the body
  • Increased production by the adrenal glands, due to a tumour or due to excessive growth of adrenal tissues (hyperplasia)
  • How is the sample collected for testing?

    Typically, blood will be taken from a vein in the arm, but sometimes urine or saliva may be tested. Blood should ideally be collected between 8-9am when blood cortisol concentrations should be at their peak. A second sample may be taken late in the evening when cortisol should be at its lowest concentration (about midnight). Samples collected at these times allow the doctor to evaluate the daily pattern of cortisol secretion (the diurnal variation). This pattern may be disrupted with excess cortisol production – the maximum amount may be at or near normal concentrations, but levels may not fall as they should throughout the day. A single morning sample may be sufficient to detect decreased concentrations of cortisol.

    Sometimes urine is tested for cortisol; this requires collecting all urine produced during a day (24-hour urine). This sample will reflect the total amount of cortisol produced in the 24 hour period but will not allow doctors to evaluate variations in cortisol secretion.

    If a saliva sample is required for testing, the sample will be collected by inserting a swab into the mouth and waiting a few minutes while the swab becomes saturated with saliva.

    NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

    Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

    Is any test preparation needed to ensure the quality of the sample?

    Some test preparation may be needed. Follow any doctor’s instructions that are given as far as timing of sample collection, resting, and/or any other specific pre-test preparation.

    A saliva test requires special care in obtaining the sample. You may be instructed to refrain from eating, drinking or brushing your teeth for a period of time (often between 15 to 30 minutes) prior to the test. Please discuss the instructions given by your local laboratory with your doctor and ensure you follow any instructions given.

    A stimulation or suppression test requires that you have a baseline blood sample drawn and are then given a specified amount of drug. Subsequent blood samples are drawn at specific times.