Arginine Vasopressin (avp, Antidiuretic Hormone) Test

Arginine vasopressin (AVP), or antidiuretic hormone (ADH), is a nonapeptide produced by the hypothalamus and released from the posterior pituitary in response to extracellular fluid hyperosmolarity and hypovolemia. AVP promotes the concentration of urine by increasing water reabsorption in the kidney tubules.Osmotic sensors in the hypothalamus react to the concentration of particles in your 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 your kidneys to store or release water to maintain a healthy range of these substances. They also regulate your body's sense of thirst. An AVP test is a simple blood test that checks the amount of ADH levels in the blood by a method called radioimmunoassay.

It is recommended that you should either wear a sleeveless or a short-sleeved shirt to make it easier for you and the technician who will be drawing the blood. Wearing a shirt with full- sleeves that can easily be rolled-up is also fine. Many medications and other substances can affect the levels of ADH in your blood. Before the test, your doctor may ask you to avoid alcohol, insulin, lithium, morphine, nicotine, steroids and diuretics. Fasting overnight may be requisite for an ADH test as well, in which case the doctor will inform you in prior.

Reference value for adults: < 4.3 pg/mL Abnormally low levels of ADH may mean pituitary damage, primary polydipsia or central diabetes insipidus, which is rare. Abnormally high levels of ADH may mean you have a brain injury or trauma, a brain or central nervous system tumor or infection, 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) or acute porphyria (which is very rare).

A band is wrapped around the arm, 3-4 inches above the collection site (superficial vein that lies within the elbow pit) A 70% alcohol pad is used to clean the skin A needle is then kept in line with and injected into a vein that can be seen from the skin The blood is dragged out from the needle by a nozzle, saved in a vessel and sealed with your name The sample is then taken to a lab for examination