Which hormone primarily affects water balance and blood pressure?

The hormone that primarily affects water balance and blood pressure is aldosterone. Aldosterone is a steroid hormone produced by the adrenal glands, specifically in the zona glomerulosa of the adrenal cortex. It plays a crucial role in the renin-angiotensin-aldosterone system (RAAS), which regulates blood volume and systemic vascular resistance, ultimately influencing blood pressure.

Aldosterone promotes the reabsorption of sodium in the kidneys. When sodium is reabsorbed, water follows osmotically, which leads to an increase in blood volume and, subsequently, blood pressure. Additionally, aldosterone causes the excretion of potassium, helping maintain electrolyte balance. This mechanism is essential for maintaining homeostasis in the body, especially in response to conditions such as low blood pressure or dehydration.

In contrast, other hormones listed do not primarily regulate water balance and blood pressure to the same extent. Cortisol, for instance, while it can influence blood pressure indirectly through its effects on metabolism and inflammation, is mainly associated with stress responses and metabolism. Adrenaline (epinephrine) is primarily involved in the fight-or-flight response, causing immediate physiological changes but not focused on long-term water balance. Thyroxine, a thyroid hormone, regulates metabolic rate and