Which hormone helps regulate the levels of salt and water in the body?

Aldosterone is the hormone that plays a crucial role in regulating the levels of salt and water in the body. It is produced by the adrenal glands and primarily influences the kidneys. Aldosterone promotes the reabsorption of sodium (salt) and the secretion of potassium into the urine. As sodium is reabsorbed, water follows by osmosis, which helps to manage blood volume and blood pressure. This function is vital in maintaining homeostasis and the balance of electrolytes.

While other hormones listed are important, they do not regulate salt and water levels in the same direct manner. Insulin primarily manages glucose metabolism, cortisol is involved in stress response and metabolism but does not have a direct role in salt and water regulation, and thyroxine primarily regulates metabolism and energy production rather than fluid balance. Therefore, the specific action of aldosterone in managing sodium and consequently water retention solidifies its role as the key hormone for this physiological function.