NBME Comprehensive Basic Science Examination (CBSE) Practice Exam

When the renin-angiotensin-aldosterone system (RAAS) is activated, the key downstream hormone that is released is aldosterone. In heart failure, reduced renal perfusion stimulates renin release, which leads to production of angiotensin II. Angiotensin II then stimulates the adrenal cortex to secrete aldosterone. Aldosterone acts on the distal tubules to increase sodium and water reabsorption, expanding extracellular fluid and preload. This helps maintain blood pressure initially but often worsens congestive symptoms in heart failure due to fluid overload.

ADH can also rise in heart failure as a response to perceived low effective arterial blood volume, but it is not the hormone produced by RAAS itself. ANP and BNP are released in response to atrial and ventricular stretch and work to counteract RAAS by promoting natriuresis and diuresis.