Which hormone is primarily involved in water reabsorption by renal tubules?

Vasopressin, also known as antidiuretic hormone (ADH), plays a crucial role in the regulation of water balance in the body, specifically by promoting water reabsorption in the renal tubules. This hormone is secreted by the posterior pituitary gland in response to high plasma osmolality or low blood volume. When vasopressin is released into the bloodstream, it acts on the kidneys, particularly the collecting ducts, increasing their permeability to water. This allows more water to be reabsorbed back into the bloodstream, resulting in concentrated urine and a reduction in urine volume.

This mechanism is vital for maintaining homeostasis regarding fluid balance and blood pressure. In conditions where the body needs to conserve water, such as dehydration, vasopressin secretion increases to help retain water.

In contrast, while aldosterone also plays a role in renal function, its primary action is to promote sodium reabsorption and potassium secretion; it indirectly influences water retention due to sodium retention but is not the primary hormone involved in water reabsorption itself. Oxytocin is more associated with functions related to childbirth and lactation rather than fluid balance. Insulin primarily regulates glucose metabolism and has a minimal direct effect on renal water re