Angiotensin II is a hormone that plays a crucial role in regulating blood pressure and fluid balance in the body. It is produced from angiotensin I through the action of an enzyme called angiotensin-converting enzyme (ACE). This hormone causes blood vessels to constrict, which increases blood pressure, and stimulates the release of aldosterone, a hormone that promotes sodium and water retention by the kidneys. In addition to its effects on blood pressure, Angiotensin II also influences the body's thirst response and can affect the release of other hormones. It is part of the renin-angiotensin-aldosterone system (RAAS), a complex system that helps maintain cardiovascular health and fluid homeostasis.