ADH
Alternative names:
antidiuretic hormone; arginine vasopressin; 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 the health care provider about drugs you are taking that may affect the test. These include acetaminophen - oral, barbiturates, cholinergic agents, estrogen, nicotine, oral hypoglycemic agents, thiazide diuretics and tricyclic antidepressants. Drugs that can decrease ADH measurements include alcohol, beta-adrenergic agents, morphine antagonists, and phenytoin.
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:
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 ADH level is suspected.
ADH is a hormone secreted from the posterior pituitary gland. It is the primary regulator of body water. ADH acts on the distal tubules in the kidneys to increase reabsorption of water. This has the effect of increasing blood volume and, secondarily, blood pressure. ADH also has a vasoconstrictor effect (that is, it constricts small blood vessels), hence its alternate name, vasopressin.
The release of ADH is controlled by the hypothalamus (an area in the brain), which contains so-called osmoreceptors. These cells sense the osmolality (concentration of particles) of extracellular fluid. When the osmolality is high, the pituitary secretes more ADH, which stimulates retention of water to dilute the body fluids. When the osmolality is low, the pituitary secretes less ADH.
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