Which hormone is responsible for water retention in the kidneys?

The hormone responsible for water retention in the kidneys is Antidiuretic Hormone (ADH), also known as vasopressin. ADH is produced in the hypothalamus and stored in the posterior pituitary gland. When the body is dehydrated or when there is an increase in plasma osmolality, ADH is released into the bloodstream.

Once in the kidneys, ADH acts primarily on the collecting ducts, increasing their permeability to water. This action allows more water to be reabsorbed back into the bloodstream rather than being excreted in the urine, resulting in concentrated urine and reduced urine output. This process is crucial for maintaining the body’s water balance and ensuring blood volume and pressure remain stable.

The other hormones listed do not primarily function in regulating water retention in the kidneys. Endorphins are primarily involved in pain relief and mood regulation. Epinephrine (adrenaline) is involved in the fight-or-flight response and affects metabolism and heart rate but is not directly related to water retention. Oxytocin plays roles in childbirth and lactation but does not influence water balance in the body.