Analysis of Urine and Body Fluids (AUBF) Practice Test 2025 – Your All-in-One Guide to Exam Success!

Aldosterone is the hormone released by the adrenal glands that plays a critical role in promoting sodium retention in the body. It acts primarily on the kidneys, specifically the distal tubules and collecting ducts, to increase the reabsorption of sodium from the urine back into the bloodstream. This action helps to regulate blood pressure, blood volume, and electrolyte balance.

When sodium is reabsorbed, water follows osmotically, leading to increased blood volume and subsequently higher blood pressure. Aldosterone secretion is stimulated by factors such as low blood sodium levels, decreased blood volume, or increased levels of angiotensin II, which is part of a feedback system that maintains homeostasis.

Other hormones listed have different primary functions. Antidiuretic Hormone (ADH), for instance, primarily regulates water balance by promoting water reabsorption in the kidneys rather than directly influencing sodium retention. Cortisol, while it can influence sodium balance, primarily serves as a stress hormone and has wider metabolic effects. Renin is an enzyme that plays a role in the renin-angiotensin-aldosterone system but is not a hormone that directly promotes sodium retention. Thus, aldosterone is the key hormone related to sodium retention in the body.