Final answer:
The hormone that modulates how much water is lost in the urine is antidiuretic hormone (ADH), which affects the collecting ducts in the kidneys. ADH adjusts water reabsorption, managing urine output based on the body's hydration needs. The renin-angiotensin-aldosterone system also plays a significant role in this process.
Step-by-step explanation:
The hormone that targets the kidneys and modulates how much water is lost in the urine is antidiuretic hormone (ADH). ADH plays a crucial role in water recovery by influencing the last 10 percent of water available for recovery after filtration at the glomerulus. This hormone acts on the collecting ducts within the kidneys, allowing them to recover varying amounts of water depending on the body's current fluid status. When the body needs to conserve water, ADH will help the kidneys reabsorb more water, reducing urine output. Conversely, when there is excess water in the body, ADH levels decrease, resulting in increased urine output and less water reabsorption.
In addition to ADH, the renin-angiotensin-aldosterone system also plays a central role in regulating water and sodium balance, which indirectly affects water loss in the urine. Renin production by the kidneys starts a cascade that leads to the production of aldosterone, which then promotes water and sodium reabsorption, aiding in the regulation of blood pressure and blood volume.