What is the role of antidiuretic hormone (ADH) in the body?

The role of antidiuretic hormone (ADH), also known as vasopressin, is primarily to maintain water levels in the body. ADH is produced in the hypothalamus and released by the posterior pituitary gland in response to increased plasma osmolality or decreased blood volume. When released into the bloodstream, ADH acts on the kidneys, specifically on the collecting ducts, to promote reabsorption of water back into the circulation. This action reduces urine output and helps to conserve water, thereby regulating hydration and maintaining the body’s fluid balance.

By increasing the permeability of the collecting ducts to water, ADH plays a crucial role in preventing dehydration and ensuring that the body's water levels remain within a healthy range. This is vital for maintaining blood volume, blood pressure, and overall cellular function. While it may indirectly influence blood pressure through its effects on blood volume and reabsorption of water, the primary action of ADH is indeed focused on water conservation and balance within the body.