ADH is plasma antidiuretic hormone, a hormone secreted by the supraoptic nucleus and paraventricular nucleus of the hypothalamus and released in the pituitary gland in response to water deprivation in the body. ADH enhances water reabsorption in renal tubules, acts as an antidiuretic, maintains plasma crystalloid osmolality, and has a large effect on renal concentrating function. Elevated values represent hypersecretion of antidiuretic hormone, hemorrhage, swelling, dehydration, malignant hypertension, etc. Decreased values represent uremia, input of large amounts of isotonic solutions, and large amounts of water intake. Changes in factors such as blood volume and blood pressure can affect antidiuretic hormone secretion.