ADH

Answer 1

Definition

ADH is a test that measures the amount of antidiuretic hormone (ADH) in blood. ADH is found in the body, and it may be given as a medication.

Alternative Names

Arginine vasopressin; Antidiuretic hormone; AVP; Vasopressin

How the test is performed

Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.

How to prepare for the test

Talk to your health care provider about your medications before the test. Many medications can affect ADH measurements, including:

• Alcohol
• Clonidine
• Diuretics
• Haloperidol
• Insulin
• Lithium
• Morphine
• Nicotine
• Steroids

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 your health care provider suspects you have a disorder that affects your ADH level.

ADH is a hormone stored in the posterior pituitary gland in the brain. It regulates water in the body. ADH acts on the kidneys to increase total body water. This increases blood volume and blood pressure.

The release of ADH is controlled by cells called osmoreceptors and baroreceptors. Osmoreceptors are specialized areas in a part of the brain called the hypothalamus.

These cells sense the concentration of particles in the blood. When the concentration is high, the pituitary releases more ADH. This causes more water to be retained to dilute the body fluids. When the concentration is low, the pituitary releases less ADH.

Special areas in the heart 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 ADH when they are high.

Certain diseases affect the normal release of ADH. The blood level of ADH must be tested to determine the cause of the disease. ADH may be measured as part of a "water restriction test" to find the cause of a disease.

Normal Values

Normal values -- 0 - 4.7 pg/mL

Note: pg/mL = picograms per milliliter

Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

What abnormal results mean

Higher-than-normal levels may indicate:

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

Lower-than-normal levels may indicate:

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

What the risks are

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

• Excessive bleeding
• Fainting or feeling light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

References

Skorecki K, Ausiello D. Disorders of sodium and water. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, PA: Saunders Elsevier; 2007: chap 117.

Verbalis JG. Posterior pituitary. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, PA: Saunders Elsevier; 2007: chap 243.

Answer 2

Definition

ADH is a test that measures the amount of antidiuretic hormone (ADH) in blood. ADH is a hormone that is produced in a part of the brain called the hypothalamus. It is then stored and released from the pituitary gland, a small gland at the base of the brain.

ADH helps manage the amount of water in the body by acting on the kidneys.

Alternative Names

Arginine vasopressin; Antidiuretic hormone; AVP; Vasopressin

How the test is performed

A blood sample is needed. For information on how this is done, see: Venipuncture

How to prepare for the test

Talk to your health care provider about your medications before the test. Many medications can affect ADH measurements, including:

• Alcohol
• Clonidine
• Diuretics
• Haloperidol
• Insulin
• Lithium
• Morphine
• Nicotine
• Steroids

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 your health care provider suspects you have a disorder that affects your ADH level. ADH helps manage the amount of water in the body by acting on the kidneys.

Your health care provider may order ADH levels if you have:

• Buildup of fluids in your body that are causing swelling or puffiness
• Excessive amounts of urine
• Low sodium ("salt") levels in your blood
• Thirst that is intense or uncontrollable

Certain diseases affect the normal release of ADH. The blood level of ADH must be tested to determine the cause of the disease. ADH may be measured as part of a "water restriction test" to find the cause of a disease.

Normal Values

Normal values for ADH can range from 1 - 5 pg/mL

Note: pg/mL = picograms per milliliter

The examples above are common measurements for results of these tests. Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or may test different specimens. Talk to your doctor about the meaning of your specific test results.

What abnormal results mean

Higher-than-normal levels may occur when too much ADH is released, either from the brain where it is made, or from somewhere else in the body. This is called syndrome of inappropriate ADH (SIADH).

Causes of SIADH include:

• Brain injury or trauma
• Brain tumors
• Fluid imbalance after surgery
• Infection in the brain or the tissue that surrounds the brain
• Infection in the lungs
• Small cell carcinoma lung cancer
• Stroke

Lower-than-normal levels may indicate:

• Damage to the pituitary gland
• Diabetes insipidus -- a condition in which the kidneys are not able to conserve water
• Primary polydipsia

What the risks are

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

• Excessive bleeding
• Fainting or feeling light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

References

Robinson AG, Verbalis JG. Posterior pituitary. In: Kronenberg HM, Melmed S, Polonsky KS, Larsen PR, eds. Williams Textbook of Endocrinology. 12th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 10.

Reviewed By

Review Date: 12/11/2011

Nancy J. Rennert, MD, Chief of Endocrinology & Diabetes, Norwalk Hospital, Associate Clinical Professor of Medicine, Yale University School of Medicine, New Haven, CT. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.