➤ Electrolyte Balance Changes in the concentration of electrolytes in the body may be due to changes in the amount of water or the amount of electrolytes. Sodium is the most common of the cations that exists in the extracellular fluid. As it is excreted through urine, it's balance in body is maintained by kidney. When the amount of sodium is decreased, aldosterone production is increased and an increased amount of sodium is re-absorbed by kidney. The secretion of the aldosterone is influenced by ACTH from Pituitary gland by a fall in the concentration of sodium in the blood and by renin produced in the kidney. ➤ Water Balance Water constituents about 60 percent of adult human body weight. It is distributed in the body in 3 main compartments, Blood Plasma- 5% of body weight. Interstitial Fluid- 11% of body weight. Intracellular Fluid- 44% of body weight. ...