What hormone decreases urine formation to aid in water retention and may increase blood pressure?

The hormone that decreases urine formation to aid in water retention and may increase blood pressure is anti-diuretic hormone, also known as vasopressin. This hormone is produced in the hypothalamus and stored in the posterior pituitary gland. Its primary function is to regulate the body's water balance by promoting water reabsorption in the kidneys, specifically in the collecting ducts. When anti-diuretic hormone is released into the bloodstream, it signals the kidneys to reabsorb more water, thereby reducing urine output and helping to retain water in the body. This mechanism is crucial for maintaining proper hydration levels, especially in situations of dehydration or high solute concentration in the blood.

As a result of increased water retention, the volume of blood in circulation can increase, potentially leading to an elevation in blood pressure. This dual role of anti-diuretic hormone aids in both fluid homeostasis and blood pressure regulation, making it a critical hormone in the context of renal and cardiovascular physiology.