At a Glance
Why Get Tested?
When to Get Tested?
When your doctor suspects excess or deficient cortisol production
Test Preparation Needed?
You may be required to rest before sample collection. For a salivary cortisol test, you may be instructed to refrain from eating, drinking, or brushing your teeth for a period of time (may be some time between 15 to 30 minutes) prior to the test. Follow any instructions you are given.
The Test Sample
What is being tested?
Cortisol is a hormone plays a role in the metabolism of proteins, lipids, and carbohydrates. It affects blood glucose levels, helps maintain blood pressure, and helps regulate the immune system. Most cortisol in the blood is bound to a protein; only a small percentage is "free" and biologically active. Free cortisol is excreted into the urine and is present in the saliva. This test measures the amount of cortisol in the blood, urine, or saliva.
The level of cortisol in the blood normally rises and falls in a "diurnal variation" pattern. It peaks early in the morning, then declines throughout the day, reaching its lowest level about midnight. This pattern can change when a person works irregular shifts (such as the night shift) and sleeps at different times of the day, and it can become disrupted when a disease or condition either limits or stimulates cortisol production.
Cortisol is produced and secreted by the adrenal glands, two triangular organs that sit on top of the kidneys. Production of the hormone is regulated by the hypothalamus in the brain and by the pituitary gland, a tiny organ located below the brain. When the blood cortisol level falls, the hypothalamus releases corticotropin-releasing hormone (CRH), which directs the pituitary gland to produce ACTH (adrenocorticotropic hormone). ACTH stimulates the adrenal glands to produce and release cortisol. In order for appropriate amounts of cortisol to be made, the hypothalamus and both the pituitary and adrenal glands must be functioning properly.
- ACTH-producing tumors, in the pituitary gland and/or in other parts of the body
- Increased production by the adrenal glands, due to a tumor or due to excessive growth of adrenal tissues (hyperplasia)
Decreased cortisol production may be seen with:
- An underactive pituitary gland or a pituitary gland tumor 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 disease.
How is the sample collected for testing?
Typically, blood will be drawn from a vein in the arm, but sometimes urine or saliva may be tested. Cortisol blood tests may be drawn at about 8 am, when cortisol should be at its peak, and again at about 4 pm, when the level should have dropped significantly. Sometimes a resting sample will be obtained late in the evening to measure cortisol when it should be at its lowest concentration in the blood (about midnight). Obtaining more than one sample allows the doctor to evaluate the daily pattern of cortisol secretion (the diurnal variation).
Sometimes urine is tested for cortisol; this usually requires collecting all of the urine produced during a day and night (a 24-hour urine) but sometimes may be done on a single sample of urine collected in the morning.
Saliva for cortisol testing is usually collected between 11 pm and midnight, the time when cortisol is normally at its lowest. The sample is usually 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 (may be some time between 15 to 30 minutes) prior to the test. Follow any specific instructions you are given.
A stimulation or suppression test requires that you have a baseline blood sample drawn and then are given a specified amount of drug. Subsequent blood samples are drawn at specified times.
Ask a Laboratory Scientist
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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.
Sources Used in Current Review
(© 1995-2011). Unit Code 8545: Cortisol, Serum. Mayo Clinic Mayo Medical Laboratories [On-line information]. Available online at http://www.mayomedicallaboratories.com/test-catalog/Overview/8545 through http://www.mayomedicallaboratories.com. Accessed September 2011.
Meikle, W. and Roberts, W. (Updated 2011 January). Adrenal Insufficiency. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/AdrenalInsufficiency.html?client_ID=LTD#tabs=0 through http://www.arupconsult.com. Accessed September 2011.
Adler, G. (Updated 2011 July 25). Cushing Syndrome. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/117365-overview through http://emedicine.medscape.com. Accessed September 2011.
(2009 May). Adrenal Insufficiency and Addison's Disease. National Endocrine and Metabolic Diseases Information Service [On-line information]. Available online at http://endocrine.niddk.nih.gov/pubs/addison/addison.aspx through http://endocrine.niddk.nih.gov. Accessed September 2011.
Eckman, A. (2009 November 23). Cortisol. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003693.htm. Accessed September 2011.
Eckman, A. (2009 November 23). Cortisol-urine. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003703.htm. Accessed September 2011.
Meikle, A. W. and Roberts, W. (Updated 2011 January). Adrenal Hyperfunction - Cushing Syndrome. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/CushingSyndrome.html through http://www.arupconsult.com. Accessed September 2011.
Pagana, K. D. & Pagana, T. J. (© 2011). Mosby’s Diagnostic and Laboratory Test Reference 10th Edition: Mosby, Inc., Saint Louis, MO. Pp 311-313.
Sources Used in Previous Reviews
MayoClinic.com. Cushings Syndrome (online information). Available online through http://www.mayoclinic.com. Accessed March 2008.
Restituto P, et.al. Advantage of salivary cortisol measurements in the diagnosis of glucocorticoid related disorders. Clin Biochem. 2008 Feb 5 [Epub ahead of print]. Available online through http://www.ncbi.nlm.nih.gov/pubmed. Accessed March 2008.
De Castro M, Moreira A. Screening and Diagnosis of Cushings Syndrome. Arq Bras Endocrinol Metab 2007;51/8.
Henry's Clinical Diagnosis and Management by Laboratory Methods. 21st ed. McPherson R, Pincus M, eds. Philadelphia, PA: Saunders Elsevier: 2007.
Pituitary Network Association. Adrenal Insufficiency (Secondary Addison's or Addison's Disease). Available online through http://www.pituitary.org/. Accessed March 2008.
Thomas, Clayton L., Editor (1997). Taber's Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition].
Pagana, Kathleen D. & Pagana, Timothy J. (2001). Mosby's Diagnostic and Laboratory Test Reference 5th Edition: Mosby, Inc., Saint Louis, MO.
Jain, T. (2004 February 2, Updated). Cortisol level. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003693.htm
(2002 June). Cushing's syndrome. NIDDK, NIH Publication No. 02-3007 [On-line information]. Available online through http://www.niddk.nih.gov
(© 2005). Cortisol, Serum or Plasma. ARUPs Guide to Clinical Laboratory Testing [On-line information]. Available online through http://www.arup-lab.com
(© 1995-2004). Cushings Syndrome. The Merck Manual Second Home Edition [On-line information]. Available online through http://www.merck.com
Raff, H. and Findling, J. (2003). A Physiologic Approach to Diagnosis of the Cushing Syndrome. Ann Intern Med. 2003;138:980-991 [on-line journal]. Available online through http://www.annals.org
Pagana K, Pagana T. (2006). Mosby's Manual of Diagnostic and Laboratory Tests. 3rd edition. St. Louis: Mosby Elsevier.