How does aldosterone influence water balance?

Aldosterone plays an important role in regulating the balance of fluids. Aldosterone is a corticosteroid, being released from the adrenal cortex (inside) of the kidney.

The release of this hormone from the adrenal cortex results in the kidneys reabsorbing more sodium and excreting more potassium. Water is reabsorbed with the the sodium (as "salt sucks"), so this, in effect, results in increased water reabsorption into the plasma, which has the effect of lowering osmotic pressure.

This means that there are high water plasma levels.