Explain how Antidiuretic Hormone (ADH) regulates bodily hydration levels

Antidiuretic hormone is produced by the hypothalamus and is released by the pituitary gland in the brain. The hypothalamus regulates the water content of the blood by controlling how much ADH is released and, subsequently, how much water is reabsorbed into the blood via the kidneys. When hydration levels in the blood fall, such as when one is dehydrated or has been producing excess sweat for example, the hypothalamus will detect this change and direct the pituitary gland to release more antidiuretic hormone into the blood. ADH targets the final segment of the nephrons in the kidneys. This segment is known as the collecting duct. The hormone increases the permeability of the surface of the collecting duct and thus increases the volume of water that is reabsorbed from inside the nephron back into the blood. The higher the concentration of ADH in the blood, the more permeable the collecting ducts are and, consequently, the more water is reabsorbed back into the blood.