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Dexamethasone Suppression of Pituitary ACTH Secretion Blood Test

Last updated Jan. 12, 2016


What are other Names for this Test? (Equivalent Terms)

  • Dexamethasone Suppression of Pituitary Adrenocorticotropic Hormone Secretion Blood Test
  • DST Blood Test

What is the Dexamethasone Suppression of Pituitary ACTH Secretion Blood Test? (Background Information)

  • Dexamethasone is a synthetic compound that structurally resembles the hormones produced by the adrenal gland (called glucocorticoids). It is administered to test the body’s ability to restore its hormonal balance when it has been disturbed
  • Adrenocorticotropic hormone (ACTH) is produced in the pituitary gland, which is situated just below the brain. ACTH stimulates the adrenal glands (small, pyramid-shaped organs located above each kidney) to produce stress hormones such as adrenaline and cortisol
  • Adrenaline, also called epinephrine, causes a number of effects that help the body respond to stress. These effects include increased heart rate and breathing, increased muscle contraction, and increased fat breakdown for energy
  • Cortisol is another stress hormone produced by the adrenal glands in response to ACTH. One effect of cortisol is to increase energy availability. It does this by stimulating the liver to produce glucose. It also does this by stimulating fat cells to release fatty acids into blood for immediate use
  • Another effect of cortisol is to suppress inflammation. It does this by inhibiting the effects of white blood cells and other components of the immune system
  • In addition to stress hormones, the adrenal glands also produce hormones that regulate electrolyte levels. These hormones include aldosterone. Electrolytes are necessary for a variety of functions, including maintaining hydration status and blood pressure
  • After ACTH causes the adrenal gland to release its various hormones, these hormones act back on the hypothalamus and pituitary glands to prevent further release of hormones. This process is called negative feedback
  • During normal conditions, the administration of dexamethasone, which is similar in nature to pituitary gland hormones, should suppress pituitary gland secretion of ACTH because of the negative feedback system. This should cause a decrease in cortisol levels in blood
  • If a low dose (2 mg) of dexamethasone does not result in decreased cortisol release, the two most likely causes are:
    • The pituitary gland may be producing excess levels of ACTH (as a result of Cushing disease)
    • ACTH is being secreted from somewhere other than the pituitary gland (like due to the presence of non-pituitary ACTH-secreting tumors)
  • To differentiate between these two possibilities, a high dose (8 mg) of dexamethasone is administered. If ACTH levels decrease, then the underlying condition is likely Cushing disease; if ACTH levels remain unchanged, then a non-pituitary ACTH-secreting tumor is suspected
  • The Dexamethasone Suppression of Pituitary ACTH Secretion Blood Test helps determine the levels of ACTH after dexamethasone has been administered. It is used to differentiate between the main causes of excessive glucocorticoid production, which are Cushing syndrome and ACTH-secreting tumors

What are the Clinical Indications for performing the Dexamethasone Suppression of Pituitary ACTH Secretion Blood Test?

Following are the clinical indications for performing the Dexamethasone Suppression of Pituitary ACTH Secretion Blood Test: 

  • Rapid weight gain, especially in the face (termed as “moon face”) and shoulders (termed as “buffalo hump”)
  • Stretch marks
  • Decreased libido
  • Acne
  • Abnormal hair growth
  • Abnormal menstrual period
  • Erectile dysfunction
  • Headache
  • Fatigue
  • Depression, mood swings, and irritability
  • Salt craving

How is the Specimen Collected for the Dexamethasone Suppression of Pituitary ACTH Secretion Blood Test?

Following is the specimen collection process for Dexamethasone Suppression of Pituitary ACTH Secretion Blood Test:

Sample required: Blood

Process of obtaining blood sample in adults:

  • A band is wrapped around the arm, 3-4 inches above the collection site (superficial vein that lies within the elbow pit)
  • The site is cleaned with 70% alcohol in an outward spiral, away from the zone of needle insertion
  • The needle cap is removed and is held in line with the vein, pulling the skin tight
  • With a small and quick thrust, the vein is penetrated using the needle
  • The required amount of blood sample is collected by pulling the plunger of the syringe out slowly
  • The wrap band is removed, gauze is placed on the collection site, and the needle is removed
  • The blood is immediately transferred into the blood container, which has the appropriate preservative/clot activator/anti-coagulant
  • The syringe and the needle are disposed into the appropriate “sharp container” for safe and hygienic disposal

Preparation required: No special preparation is needed prior to the test.

What is the Significance of the Dexamethasone Suppression of Pituitary ACTH Secretion Blood Test Result?

  • A low ACTH value for the low-dose (2 mg) Dexamethasone Suppression of Pituitary ACTH Secretion Blood Test may indicate Cushing syndrome
  • A low ACTH value for the high-dose (8 mg) Dexamethasone Suppression of Pituitary ACTH Secretion Blood Test may indicate non-pituitary ACTH-secreting tumor

The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.

Additional and Relevant Useful Information:

  • Certain factors, such as the external intake of ACTH, may interfere with the results of the Dexamethasone Suppression of Pituitary ACTH Secretion Blood Test

Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider of the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.

What are some Useful Resources for Additional Information?

The following DoveMed website links are useful resources for additional information: 

http://www.dovemed.com/common-procedures/procedures-laboratory/acth-stimulation-blood-test/

http://www.dovemed.com/adrenocorticotropic-hormone-blood-test/

Please visit our Laboratory Procedures Center for more physician-approved health information:

http://www.dovemed.com/common-procedures/procedures-laboratory/

References and Information Sources used for the Article:

Kee, J. L. (2010). Laboratory and diagnostic tests with nursing implications (8th ed.). Upper Saddle River, NJ: Pearson.

Martini, F., Nath, J. L., & Bartholomew, E. F. (2012). Fundamentals of anatomy & physiology (9th ed.). San Francisco: Benjamin Cummings.

Mayo Clinic. (2013, March 28). Cushing syndrome. Retrieved from http://www.mayoclinic.org/

Williamson, M. A., Snyder, L. M., & Wallach, J. B. (2011). Wallach's interpretation of diagnostic tests (9th ed.). Philadelphia: Wolters Kluwer/Lippincott Williams & Wilkins.

Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: Jan. 12, 2016
Last updated: Jan. 12, 2016