What are the other Names for this Test? (Equivalent Terms)
- ADH (Antidiuretic Hormone) Test
- Arginine Vasopressin (AVP) Test
- Vasopressin Test
What is Antidiuretic Hormone (ADH) Test? (Background Information)
- An Antidiuretic Hormone (ADH) Test measures the amount of ADH in blood. ADH is secreted by the hypothalamus gland (a part of the brain) and stored in the pituitary gland. The pituitary gland is a small ‘hormone-secreting and storing’ endocrine gland, located at the base of the brain (in the center)
- When ADH is released from the pituitary gland into blood, it acts on the kidneys and helps reabsorb water into the body, during urine formation. When the body needs water, more ADH is released from the pituitary, to reabsorb more water into the kidneys, leading to the formation of concentrated urine
- On the other hand, if the body wants to get rid of water (during high intake of water situations), less ADH is released and less water is reabsorbed into the body. This causes the formation of dilute urine. Hence, ADH determines how much urine is produced by the body
What are the Clinical Indications for performing the Antidiuretic Hormone (ADH) Test?
An Antidiuretic Hormone Test may be ordered as a stand-alone test, or as part of diagnostic work-up, whenever a healthcare provider suspects water excess or deprivation.
- ADH levels may be increased in some conditions. Such conditions include:
- Pathological (disease-related) changes in hypothalamus or pituitary
- Tumors of the pituitary
- Brain stroke
- Severe dehydration in the body
- Major surgery
- Severe infections
- Certain cancers in the body, such as small-cell carcinoma of lung
- Abnormal increase in ADH production in the body results in a condition called SIADH (syndrome of inappropriate ADH). In chronic cases of water intoxication, symptoms may not be present. However, acute cases of SIADH may be present with:
- Nausea and vomiting
- Severe cases may lead to coma
- ADH deficiency leads to a condition called diabetes insipidus, signs of which include increased thirst and frequent urination
ADH Testing may be performed under these (above-mentioned) conditions, but a diagnosis is mainly made on the basis of clinical signs and symptoms, combined with other lab tests, like blood and urine electrolytes (minerals such as sodium, potassium, and chlorine) and fluid concentration of the body
How is the Specimen Collected for Antidiuretic Hormone (ADH) Test?
Sample required: Blood
Process: Insertion of needle into a vein (arm).
Preparation required: None. Many medications may affect the test results; hence, the healthcare provider must be informed about all medications that are being currently taken.
What is the Significance of the Antidiuretic Hormone (ADH) Test Result?
The results of Antidiuretic Hormone Test in itself, does not constitute a diagnosis. The results have to be evaluated in conjunction with the medical history, signs and symptoms, and other lab test results.
- The normal values of the test can range from 1-5 pg/ml (picogram per milliliter). However, the results may vary according to the age, gender, blood concentration, and with respect to the individual laboratory, where the tests are conducted. The healthcare provider evaluates the test results taking into consideration, all these various factors
- The test is performed along with other lab tests to help diagnose cases of water excess (SIADH), or water deprivation (diabetes insipidus)
- It can be also used to measure the success of treatment, or may be performed as a routine screening procedure, to establish baseline values
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:
Diabetes insipidus may be of the following types:
- Central-type diabetes insipidus: A condition, which causes decreased formation or release of less quantities of Antidiuretic Hormone from the hypothalamus, or pituitary respectively, due to some pathology in these tissues. This may occur because of conditions, like a tumor, trauma, injury, infection, or some kind of genetic defect
- Nephrogenic diabetes insipidus: A condition, in which the kidneys fail to reabsorb water, in response to ADH
Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider, 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.
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References and Information Sources used for the Article
http://www.nlm.nih.gov/medlineplus/ency/article/003702.htm (accessed on 04/05/2013)
http://www.umm.edu/ency/article/003702.htm (accessed on 04/05/2013)
http://labtestsonline.org/understanding/analytes/adh/tab/test (accessed on 04/05/2013)