Antidiuretic hormone

Antidiuretic hormone (ADH), or arginine vasopressin (AVP), is a peptide hormone produced by the hypothalamus, and stored in the posterior pituitary gland. ADH acts on the kidneys, concentrating the urine by promoting the reabsorption of water and salt into the cortical collecting duct.

ADH is activated by "water receptors" in both the extracellular fluid volume and the intracellular fluid volume. Ethanol and caffeine block the release of ADH from the posterior pituitary gland. This decrease in water reabsorption leads to a higher volume of urine output.

In the extracellular fluid the activators are maily baroreceptors in the veins, atria, and arterioles. In the intracellular fluid the activators are mainly osmoreceptors in the hypothalamus.