At a Glance
Why Get Tested?
To help detect, diagnose, and determine the cause of antidiuretic hormone (ADH) deficiency or excess; to investigate low blood sodium levels (hyponatremia); to distinguish between the two types of diabetes insipidus
When to Get Tested?
When you have hyponatremia or have persistent thirst, frequent urination, and dehydration
A blood sample drawn from a vein in your arm
Test Preparation Needed?
None needed for an ADH test; however, talk to your doctor about required preparation when the ADH test is performed as part of a water deprivation ADH stimulation test or a water loading ADH suppression test.
The Test Sample
What is being tested?
The ADH test measures the amount of antidiuretic hormone (ADH) in the blood. ADH, also called arginine vasopressin (AVP), is a hormone produced by the hypothalamus and stored in the posterior pituitary gland. Antidiuretic hormone helps regulate water balance in the body by controlling the amount of water the kidneys reabsorb.
ADH is normally released by the pituitary in response to sensors that detect increases in blood osmolality or decreases in blood volume. The kidneys react to ADH by conserving water and producing urine that is more concentrated. The retained water dilutes the blood, lowers its osmolality, and increases blood volume and pressure. If this is not sufficient to restore the water balance, then thirst is also stimulated so that the affected person will drink more water.
There are a variety of disorders, conditions, and medications that can affect either the amount of ADH released or the kidneys' sensitivity to it. ADH deficiency and excess can cause acute and chronic symptoms that, in rare cases, may become life-threatening. If there is too little ADH or the kidneys do not respond to ADH, then too much water is lost through the kidneys, the urine produced is more dilute than normal, and the blood becomes more concentrated. This can cause excessive thirst, frequent urination, dehydration, and high blood sodium (hypernatremia). If there is too much ADH, then water is retained, blood volume increases, and the person may experience nausea, headaches, disorientation, lethargy, and hyponatremia.
The ADH test is not widely used to diagnose these conditions. Often, a diagnosis is made on the basis of clinical history and other laboratory tests such as urine and blood osmolality and electrolytes.
ADH deficiency is called diabetes insipidus. There are two types of this disorder: central and nephrogenic. Central diabetes insipidus is associated with a lack of ADH production by the hypothalamus or release from the pituitary and may be due to a variety of causes, including an inherited genetic defect, head trauma, a brain tumor, or due to an infection that causes encephalitis or meningitis. Nephrogenic diabetes insipidus originates in the kidney and is associated with a lack of response to ADH, causing an inability to concentrate urine. It may be inherited or caused by a variety of kidney diseases. Both types of diabetes insipidus lead to the excretion of large quantities of dilute urine.
Increased levels of ADH are often seen with "syndromes of inappropriate antidiurectic hormone" (SIADH). SIADH is characterized by production of too much ADH, resulting in water retention, hyponatremia, and decreased blood osmolality. It may be due to a wide number of diseases and conditions that either stimulate excessive ADH production and release or that prevent its suppression. SIADH may also be seen with cancers that produce ADH or ADH-like substances independent of the hypothalamus and pituitary glands. Regardless of the cause or source, excessive ADH causes low blood sodium and osmolality because water is retained and blood volume is increased.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm.
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?
No test preparation is needed for an ADH test. However, talk to your doctor about required preparation when the ADH test is performed as part of a water deprivation ADH stimulation test or a water loading ADH suppression test.
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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.
Pagana, K. D. & Pagana, T. J. (© 2007). Mosby's Diagnostic and Laboratory Test Reference 8th Edition: Mosby, Inc., Saint Louis, MO. Pp 76-78.
Clarke, W. and Dufour, D. R., Editors (© 2006). Contemporary Practice in Clinical Chemistry: AACC Press, Washington, DC. Pp 133.
Eckman, A. (Updated 2009 October 14). ADH. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003702.htm through http://www.nlm.nih.gov. Accessed February 2010.
Patel, P. (Updated 2009 October 14). Diabetes insipidus. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000377.htm through http://www.nlm.nih.gov. Accessed February 2010.
Ferry, R. et. al. (Updated 2009 October 22). Syndrome of Inappropriate Antidiuretic Hormone Secretion. Emedicine [On-line information]. Available online at http://emedicine.medscape.com/article/924829-overview through http://emedicine.medscape.com. Accessed February 2010.
Deshmukh, S. and Thomas, C. (Updated 2009 May 28). Syndrome of Inappropriate Secretion of Antidiuretic Hormone. eMedicine [On-line information]. Available online at http://emedicine.medscape.com/article/246650-overview through http://emedicine.medscape.com. Accessed February 2010.
Resnick, B. (2009 December 28). What Causes Hyponatremia in an Elderly Patient? Medscape Today [On-line information]. Available online at http://www.medscape.com/viewarticle/714108 through http://www.medscape.com. Accessed February 2010.
Lewis, J. (Revised 2009 May). Water and Sodium Balance Merck Manual for Healthcare Professionals [On-line information]. Available online at http://www.merck.com/mmpe/sec12/ch156/ch156b.html?qt=ADH&alt=sh through http://www.merck.com. Accessed February 2010.
Lewis, J. (Revised 2009 May). Hyponatremia. Merck Manual for Healthcare Professionals [On-line information]. Available online at http://www.merck.com/mmpe/sec12/ch156/ch156d.html through http://www.merck.com. Accessed February 2010.
Mayo Clinic staff (2009 July 14) Hyponatremia. MayoClinic.com [On-line information]. Available online at http://www.mayoclinic.com/health/hyponatremia/DS00974 through http://www.mayoclinic.com. Accessed February 2010.
(Revised 2009 February 17). Detailed Guide: Pituitary Tumor, What Are Pituitary Tumors? American Cancer Society [On-line information]. Available online at http://www.cancer.org/docroot/CRI/content/CRI_2_4_1x_What_Are_Pituitary_Tumors_61.asp?sitearea= through http://www.cancer.org. Accessed February 2010.
Kasper DL, Braunwald E, Fauci AS, Hauser SL, Longo DL, Jameson JL eds, (2005). Harrison's Principles of Internal Medicine, 16th Edition, McGraw Hill, Pp 2097-2102.
Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Burtis CA, Ashwood ER, Bruns DE, eds. St. Louis: Elsevier Saunders; 2006, Pp 1992-1996.