Health Encyclopedia

ADH

Definition

ADH is a test that measures the amount of ADH in serum. ADH is a hormone found in the body. It may also be given as a medication.

Alternative Names

Arginine vasopressin; Antidiuretic hormone; AVP; Vasopressin

How the test is performed

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic. An elastic band is placed around the upper arm to apply pressure and cause the vein to swell with blood.

A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

For infants or young children:

The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. A bandage may be applied to the puncture site if there is any bleeding.

How to prepare for the test

Consult your health care provider about your medications before the test. Many medications, including nicotine, insulin, diuretics, lithium, morphine, alcohol, steroids, haloperidol, and clonidine can affect ADH measurements.

How the test will feel

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed

This test is performed if a disorder that affects the ADH level is suspected.

ADH is a hormone stored in the posterior pituitary gland in the brain. It is the primary regulator of water in the body. ADH acts on the kidneys to increase total body water. This decreases the plasma concentration, increasing blood volume and increasing blood pressure.

The release of ADH is controlled by cells, called osmoreceptors and baroreceptors. Osmoreceptors are specialized areas in the hypothalamus (an area in the brain). These cells sense the concentration of particles in the blood. When the concentration is high, the pituitary releases more ADH. This stimulates retention of water to dilute the body fluids. When the concentration is low, the pituitary releases less ADH.

Baroreceptors are specialized areas in the heart that sense blood volume and blood pressure. The heart signals the pituitary to release more ADH when blood volume or blood pressure are low and less when they are high.

In certain diseases, the normal release of ADH is altered, and the serum level of ADH must be tested to determine the cause. ADH may be measured as part of a "water restriction test" to more thoroughly investigate the cause of a disease.

Normal Values

Values of 0 to 4.7 pg/mL are normal. Normal value ranges may vary slightly among different laboratories.

Note: pg/ml = picograms per milliliter

What abnormal results mean

Higher-than-normal levels may indicate:

Acute porphyria (very rare)
Central nervous system infection
Central nervous system tumor
Post-surgery fluid imbalance
SIADH (syndrome of inappropriate ADH)
Pulmonary infections
Pulmonary or mediastinal tumors

Lower-than-normal levels may indicate:

Damage to the pituitary gland
Diabetes insipidus -- central or nephrogenic
Primary polydipsia

What the risks are

Excessive bleeding
Fainting or feeling lightheaded
Hematoma (blood accumulating under the skin)
Infection (a slight risk any time the skin is broken)
Multiple punctures to locate veins

Special considerations

There are none.

Review Date:3/8/2006
Reviewed By:Robert Hurd, M.D., Department of Biology, College of Arts and Sciences, Xavier University, Cincinnati, OH. Review provided by VeriMed Healthcare Network.

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