ADH

Definition:

A test that measures the amount of ADH in serum. (Note: ADH is a normal body hormone; it can also be given as a medication.)

Alternative Names:

Arginine vasopressin; Antidiuretic hormone; AVP; Vasopressin

How the test is performed:

Adult or child:
Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and a tourniquet (an elastic band) or blood pressure cuff is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the tourniquet to distend (fill 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 tourniquet 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.

Infant or young child:
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. Cotton or a bandage may be applied to the puncture site if there is any continued 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.

Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experience, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:

infant test or procedure preparation (birth to 1 year)
toddler test or procedure preparation (1 to 3 years)
preschooler test or procedure preparation (3 to 6 years)
schoolage test or procedure preparation (6 to 12 years)
adolescent test or procedure preparation (12 to 18 years)

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 he ADH level is suspected.

ADH is a hormone stored in the posterior pituitary gland in the brain. It is the primary regulator of body water. ADH acts on the kidneys to increase total body water. This has the effect of decreasing 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 necessitating the need to test the serum level of ADH

Normal Values:

Values of 0 to 4.7 pg/mL are normal.

Note: pg/ml = picograms per milliliter

What abnormal results mean:

Greater-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

Low values 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

Review Date: 2/16/2002
Reviewed By: Mary D Ruppe, M.D., Division of Endocrinology and Metabolism, Johns Hopkins Hospital, Baltimore, MD. Review provided by the VeriMed Healthcare Network

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