(See also Overview of Electrolytes Overview of Electrolytes Well over half of the body's weight is made up of water. Doctors think about the body's water as being restricted to various spaces, called fluid compartments. The three main compartments are... read more and Overview of Phosphate's Role in the Body Overview of Phosphate's Role in the Body Phosphorus is an element that plays an important role in the body. In the body, almost all phosphorus is combined with oxygen, forming phosphate. Phosphate is one of the body's electrolytes... read more .)
Phosphate is one of the body's electrolytes Overview of Electrolytes Well over half of the body's weight is made up of water. Doctors think about the body's water as being restricted to various spaces, called fluid compartments. The three main compartments are... read more , which are minerals Overview of Minerals Minerals are necessary for the normal functioning of the body’s cells. The body needs relatively large quantities of Calcium Chloride Magnesium Phosphate read more 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 Overview of Kidney Failure This chapter includes a new section on COVID-19 and acute kidney injury (AKI). Kidney failure is the inability of the kidneys to adequately filter metabolic waste products from the blood. Kidney... read more . In these people, the kidneys do not excrete enough phosphate Overview of Phosphate's Role in the Body Phosphorus is an element that plays an important role in the body. In the body, almost all phosphorus is combined with oxygen, forming phosphate. Phosphate is one of the body's electrolytes... read more . 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 parathyroid hormone Overview of Calcium's Role in the Body ( hypoparathyroidism Hypoparathyroidism Hypoparathyroidism is a deficiency of parathyroid hormone (PTH) often caused by an autoimmune disorder, treatment-related damage to the parathyroid glands, or removal of the glands during surgery... read more )
Lack of response to a normal level of parathyroid hormone (pseudohypoparathyroidism)
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) Hypocalcemia (Low Level of Calcium in the Blood) In hypocalcemia, the calcium level in blood is too low. A low calcium level may result from a problem with the parathyroid glands, as well as from diet, kidney disorders, or certain drugs. As... read more . 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 Atherosclerosis Atherosclerosis is a condition in which patchy deposits of fatty material (atheromas or atherosclerotic plaques) develop in the walls of medium-sized and large arteries, leading to reduced or... read more (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
Drugs 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.
Drugs that bind with phosphate, such as sevelamer, lanthanum, and calcium compounds, should be taken with meals as prescribed by a doctor. These drugs make phosphate harder to absorb, and more phosphate is excreted. Sevelamer and lanthanum are often used for people undergoing dialysis because calcium compounds can make calcium-phosphate crystals more likely to form in tissues.