In hyperphosphatemia, the level of phosphate in blood is too high.
(See also Overview of Electrolytes and Overview of Phosphate's Role in the Body.)
Phosphate is one of the body's electrolytes, which are minerals that carry an electric charge when dissolved in body fluids such as blood, but the majority of phosphate in the body is uncharged.
Hyperphosphatemia is rare except in people with severe kidney dysfunction. In these people, the kidneys do not excrete enough phosphate. Dialysis, often used to treat kidney dysfunction, is not very effective at removing phosphate and thus does not reduce the risk of hyperphosphatemia.
Less commonly, hyperphosphatemia develops in people with the following:
A low level of (hypoparathyroidism)
Lack of response to a normal level of parathyroid hormone (pseudohypoparathyroidism)
Crush injuries
Destruction of muscle tissue (rhabdomyolysis)
Severe bodywide infections (sepsis)
Large amounts of phosphate taken by mouth or given in an enema
Symptoms of Hyperphosphatemia
Most people with hyperphosphatemia do not have symptoms. However, in people with severe kidney dysfunction, calcium combines with phosphate, which lowers calcium levels in the blood (a disorder called hypocalcemia). Low calcium can cause muscle cramps and spasms but also causes an increase in parathyroid hormone levels, resulting in bone weakness and other problems.
The calcium and phosphate also can form crystals (calcify) in body tissue, including within the walls of the blood vessels. Severe arteriosclerosis (hardening of the arteries) can result, leading to strokes, heart attacks, and poor circulation.
Crystals can also form in the skin, where they cause severe itching.
Diagnosis of Hyperphosphatemia
Measurement of phosphate levels in the blood
The diagnosis of hyperphosphatemia is based on blood tests indicating that the phosphate level is high.
Treatment of Hyperphosphatemia
A diet low in phosphate
Medications to increase phosphate excretion
In people with kidney dysfunction, hyperphosphatemia is treated by reducing consumption of phosphate and reducing absorption of phosphate from the digestive tract. Foods that are high in phosphate, such as milk, egg yolks, chocolate, and soft drinks, should be avoided.
calciumcalcium compounds can make calcium-phosphate crystals more likely to form in tissues.
