Which hormone is involved in regulating fluid balance and blood pressure by stimulating vasoconstriction?

The hormone that plays a crucial role in regulating fluid balance and blood pressure through the mechanism of vasoconstriction is renin. Renin is an enzyme produced by the juxtaglomerular cells of the kidneys in response to low blood pressure or low sodium concentration.

When released, renin converts angiotensinogen, a protein produced by the liver, into angiotensin I. This substance is subsequently transformed into angiotensin II, which is a potent vasoconstrictor. Angiotensin II causes blood vessels to narrow, increasing vascular resistance and, consequently, raising blood pressure. Additionally, angiotensin II acts on the adrenal glands to stimulate the release of aldosterone, which promotes sodium reabsorption in the kidneys, further supporting fluid balance and blood pressure regulation.

Understanding the role of renin in this context helps clarify its significance in the renin-angiotensin-aldosterone system (RAAS), which is a critical regulator of both renal function and cardiovascular health.