Aldosterone's primary function includes which of the following?

Aldosterone's primary function is to promote the reabsorption of sodium in the kidneys. It acts mainly on the distal convoluted tubule and the collecting ducts, where it increases the activity of sodium channels and sodium-potassium ATPase pumps. As a result, more sodium is reabsorbed back into the bloodstream, leading to an increase in blood volume and blood pressure. This process is essential for the regulation of fluid and electrolyte balance in the body.

Furthermore, aldosterone also influences the excretion of potassium, making it essential for maintaining proper potassium levels in the blood. However, it does not inhibit potassium reabsorption outright; rather, it promotes the secretion of potassium into the urine as sodium is reabsorbed.

While calcium absorption and chloride secretion are important functions in the body, they are not directly influenced by aldosterone. Thus, promoting sodium reabsorption accurately describes aldosterone's primary role in fluid and electrolyte homeostasis.