vasopresszin

Vasopressin, also known as antidiuretic hormone (ADH) or arginine vasopressin (AVP), is a hormone produced by the hypothalamus and released by the posterior pituitary gland. It plays a crucial role in regulating the body's water balance and blood pressure.

The primary function of vasopressin is to increase water reabsorption in the kidneys. When the body is dehydrated or blood pressure drops, the hypothalamus signals the release of vasopressin. This hormone travels to the kidneys and binds to receptors in the collecting ducts, making them more permeable to water. As a result, more water is reabsorbed from the filtrate back into the bloodstream, concentrating the urine and reducing water loss. This mechanism is vital for maintaining hydration and preventing dehydration.

In addition to its antidiuretic effects, vasopressin also acts as a vasoconstrictor, meaning it narrows blood vessels. This action helps to increase blood pressure, which is particularly important during states of low blood volume or shock. The combined effects of water retention and vasoconstriction help to stabilize blood pressure and ensure adequate blood flow to vital organs.

The secretion of vasopressin is tightly regulated by osmolality (the concentration of solutes in the blood) and blood volume. High osmolality or low blood volume stimulates vasopressin release, while low osmolality or high blood volume suppresses it. Disruptions in vasopressin production or its action can lead to various medical conditions, such as diabetes insipidus, which is characterized by excessive thirst and urination.