Medical Health Encyclopedia

ADH

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:

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This test is performed if a disorder that affects the 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 decreases 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, and the serum level of ADH must be tested to determine the cause.

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