BLOOD PRESSURE REGULATOR
Kidneys also play a role in controlling the blood pressure. Not only they maintain the balance of fluids, kidneys react to low blood presure by releasing the hormone renin, which sets off a cascade of actions that promotes water retention.
However, kidneys are at the receiving end of changes in blood pressure. High blood pressure not only damages the kidneys, but may escalate further when the kidneys are damaged and unable to excrete fluids. Thus, the kidney has an important role in keeping blood pressure at normal levels.
High blood pressure of hypertension causes the heart to work harder to pump blood throughout the body. Over time, this causes significant damage to blood vessels. Once the blood vessels within the kidney are damaged, the other functions of this organ become impaired and can no longer get rid of waste and excess fluid efficiently. The excess fluid within the body further increases blood pressure levels.
The kidneys also help maintain a proper balance of calcium and phosphorus in the blood. Renal osteodystrophy is a disease that results when kidneys fail to carry out this function.
Healthy kidneys produce a type of vitamin D known as calcitriol. Calcitriol promotes calcium absorption from food into the blood and bones, and works with the parathyroid hormone to maintain a normal balance of calcium in the body.
But when damaged kidneys are unable to produce calcitriol to absorb calcium from food, the parathyroid hormone level increases. The parathyroid hormone in turn, strips calcium from bones to maintain body's calcium levels as it is unable to. Prolonged removal of calcium from the body's storage can result in brittle bones and osteporosis.