Which hormone is essential to our ability to maintain our fluid levels?

Aldosterone is the hormone that is important to maintain the fluid levels. It is a mineralcorticoid hormone that regulates the electrolyte as well as the water balance by helping in retention of sodium and water and excretes potassium. This then causes the blood pressure to increase.

I’m not exactly sure what your trying to ask, but if it’s how an organelle is similar to a body system or a part a nucleus is like a in function. but i don’t fully understand what you’re trying to ask