Antidiuretic hormone

Antidiuretic hormone (ADH), also known as vasopressin, is a hormone produced in the hypothalamus and stored in the posterior pituitary gland. It plays a crucial role in maintaining the balance of water in the body by controlling the amount of water the kidneys reabsorb while they are filtering wastes out of the blood.

Function

The primary function of the antidiuretic hormone is to conserve the body's water by reducing the amount of water passed out in the urine. A high concentration of ADH leads to the production of more concentrated urine. In contrast, a low concentration of ADH results in the production of more diluted urine.

ADH also plays a role in raising blood pressure by constricting the arterioles, small blood vessels that branch off an artery going to the tissues and organs.

Regulation

The secretion of ADH is regulated by the osmoreceptors, sensory receptors in the hypothalamus that detect changes in the osmotic pressure of the blood. When the osmotic pressure of the blood is high, indicating dehydration, the osmoreceptors signal the hypothalamus to produce and release more ADH. Conversely, when the osmotic pressure is low, indicating an excess of water, less ADH is produced and released.

Disorders

Disorders related to ADH include diabetes insipidus, a condition characterized by excessive thirst and excretion of large amounts of severely diluted urine, and syndrome of inappropriate antidiuretic hormone (SIADH), a condition where the body produces too much ADH, leading to water retention and low sodium levels in the blood.

See also

• Osmoregulation
• Endocrine system
• Hypothalamus
• Pituitary gland