What is the main role of aldosterone in the body?

Aldosterone is a steroid hormone produced by the adrenal cortex and plays a crucial role in the regulation of electrolyte and water balance in the body. Its primary function is to enhance sodium reabsorption in the kidneys, specifically in the distal tubules and collecting ducts. By promoting sodium retention, aldosterone also leads to water retention because water follows sodium due to osmotic forces.

This action is vital for maintaining blood volume and, consequently, blood pressure. Increased blood volume contributes to higher blood pressure, which is an essential factor in ensuring adequate perfusion of tissues and organs. Furthermore, aldosterone also promotes the excretion of potassium, helping to maintain electrolyte balance.

In contrast, the other options describe functions that are not directly related to aldosterone. For example, regulating blood sugar levels is primarily the role of insulin and glucagon. The production of red blood cells is influenced mainly by erythropoietin, driven by factors such as oxygen levels. Increasing metabolic rate is primarily controlled by thyroid hormones, not aldosterone. Therefore, the main role of aldosterone is indeed to control water retention and blood pressure, reflecting its importance in fluid and electrolyte homeostasis.