Antidiuretic Hormone (ADH) Test

ADH is also called arginine vasopressin. It’s a hormone made by the hypothalamus in the brain and stored in the posterior pituitary gland. It tells the kidneys how much water to conserve. ADH constantly regulates and balances the amount of water in blood. Higher water concentration increases the volume and pressure of the blood. Osmotic sensors and baroreceptors work with ADH to maintain water metabolism. Osmotic sensors in the hypothalamus react to the concentration of particles in blood. These particles include molecules of sodium, potassium, chloride, and carbon dioxide. When particle concentration isn’t balanced, or blood pressure is too low, these sensors and baroreceptors tell the kidneys to store or release water to maintain a healthy range of these substances. They also regulate the body’s sense of thirst.

The normal range for ADH is 1-5 picograms per milliliter (pg/mL). Normal ranges can vary slightly among different laboratories. ADH levels that are too low or too high can be caused by a number of different problems.

ADH deficiency

Too little ADH in your blood may be caused by compulsive water drinking or low blood serum osmolality, which is the concentration of particles in your blood.

A rare water metabolism disorder called central diabetes insipidus is sometimes the cause of ADH deficiency. Central diabetes insipidus is marked by a decrease in either the production of ADH by your hypothalamus or the release of ADH from your pituitary gland.

Common symptoms include excessive urination, which is called polyuria, followed by extreme thirst, which is called polydipsia.

People with central diabetes insipidus are often extremely tired because their sleep is frequently interrupted by the need to urinate. Their urine is clear, odorless, and has an abnormally low concentration of particles.

Central diabetes insipidus can lead to severe dehydration if it’s left untreated. Your body won’t have enough water to function.

This disorder is not related to the more common diabetes, which affects the level of the hormone insulin in your blood.

Excess ADH

When there’s too much ADH in your blood, syndrome of inappropriate ADH (SIADH) may be the cause. If the condition is acute, you may have a headache, nausea, or vomiting. In severe cases, coma and convulsions can occur. Increased ADH is associated with: leukemia and other cancers Guillain-Barré syndrome multiple sclerosis epilepsy acute intermittent porphyria, which is a genetic disorder that affects your production of heme, an important component of blood cystic fibrosisemphysema tuberculosis HIV AIDS Dehydration, brain trauma, and surgery can also cause excess ADH.

Nephrogenic diabetes insipidus is another very rare disorder that may affect ADH levels. If you have this condition, there’s enough ADH in your blood, but your kidney can’t respond to it, resulting in very dilute urine. The signs and symptoms are similar to central diabetes insipidus. They include excessive urination, which is called polyuria, followed by extreme thirst, which is called polydipsia. Testing for this disorder will likely reveal normal or high ADH levels, which will help distinguish it from central diabetes insipidus.

Nephrogenic diabetes insipidus is not related to the more common diabetes mellitus, which affects the level of insulin hormone in the blood.

Abnormally high levels of ADH may mean you have:

• a brain injury or trauma
• a brain tumor
• a brain infection
• a central nervous system infection or tumor
• a lung infection
• small cell carcinoma lung cancer
• fluid imbalance after surgery
• syndrome of inappropriate ADH (SIADH)
• a stroke
• nephrogenic diabetes insipidus, which is very rare
• acute porphyria, which is very rare

Abnormally low levels of ADH may mean:

• pituitary damage
• primary polydipsia
• central diabetes insipidus, which is rare

An ADH test alone is usually not enough to make a diagnosis. Your doctor will probably need to perform a combination of tests. Some tests that may be performed with an ADH test include the following:

• An osmolality test is a blood or urine test that measures the concentration of dissolved particles in your blood serum and urine.
• An electrolyte screening is a blood test that’s used to measure the amount of electrolytes, usually sodium or potassium, in your body.
• A water deprivation test examines how frequently you urinate if you stop drinking water for several hours.

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