Which hormone is primarily involved in the regulation of sodium balance and blood pressure?

Aldosterone is a steroid hormone produced by the adrenal cortex and plays a crucial role in maintaining sodium balance in the body and regulating blood pressure. It acts primarily on the kidneys, promoting the reabsorption of sodium ions back into the bloodstream while facilitating the excretion of potassium ions. This sodium reabsorption increases the osmolarity of the blood, leading to an increase in water retention, which in turn raises blood volume and, consequently, blood pressure.

The importance of aldosterone in the renin-angiotensin-aldosterone system (RAAS) underlines its role in the body's response to low blood pressure or low sodium levels. When blood pressure drops, the kidneys release renin, which initiates a cascade that ultimately leads to increased levels of aldosterone. This response is vital for maintaining cardiovascular health and fluid balance.

The other hormones mentioned, while they have significant roles in various physiological processes, do not primarily regulate sodium balance and blood pressure in the manner that aldosterone does. Adrenocorticotropic hormone stimulates cortisol production, which has many effects on metabolism and stress responses but is not focused specifically on sodium balance. Cortisol can influence sodium levels indirectly, but it is not its primary function. Insulin primarily regulates glucose