Phosphates play a crucial role in the organism for the maintenance of many life processes. Phosphate metabolism and calcium metabolism are closely related. Both a phosphate deficiency and a phosphate excess cause severe health complaints, which can also lead to death.
What is phosphate metabolism?
Phosphates, as anions of phosphoric acid, are involved in all metabolic processes in the body. Phosphates are involved as anions of phosphoric acid in all metabolic processes in the body. They are a component of the genetic material DNA and RNA, of energy-rich intermediate compounds such as ATP and ADP and, in combination with calcium of hydroxyapatite, in bones and teeth. In the form of ATP, they play an important role in energy metabolism. Phosphate metabolism is closely linked to calcium metabolism. If the phosphate content in the blood increases, the calcium content decreases at the same time and vice versa. The main amount of phosphate in the organism, about 85 percent, is stored in the bones and teeth. The bones in particular serve as phosphate stores. Approximately 14 percent of the phosphates are found inside the cells. There they serve, as components of DNA, RNA, the energy transmitters ATP and ADP as well as in the cell membranes, as phospholipids. Phosphates are constantly absorbed through food and excreted through the kidneys. In the process, a balance is formed. Fluctuations in phosphate levels are balanced by a complicated interplay of hormones, such as parathormone, calcitonin as well as vitamin D, and the|excretory function of the kidneys. Approximately 500 to 1000 milligrams of phosphate are absorbed daily from food. The normal plasma level of phosphates is approximately 1.4 to 2.7 mval/l.
Function and role
Phosphates possess several important functions in the organism. For example, they are involved in the formation of bones and teeth. Furthermore, they link the individual nucleotides of DNA and RNA to form a polymeric hereditary molecule. As a component of ATP, they serve as energy stores and energy transmitters in many chemical reactions in metabolism. Thus, they are indispensable in both energy and building metabolism. Moreover, many biochemical conversions can only take place at all through the transfer of phosphate groups. The skeletal system serves as the organism’s largest phosphate and calcium store. The bones and teeth are made of hydroxyapatite. Hydroxyapatite is a modified calcium phosphate. When there is an increased need for calcium, the action of parathyroid hormone initiates processes that release phosphates and calcium from the bones. Since parathyroid hormone is mainly responsible for supplying the body with calcium, it also promotes phosphate excretion via the kidneys. This is because if the concentration of both calcium and phosphates were to increase simultaneously, calcium phosphate would precipitate. This, in turn, would lower the calcium concentration. In this sense, phosphate metabolism cannot be separated from calcium metabolism. As a rule, the phosphate content in the blood plasma is sufficient to perform all metabolic functions. In the case of phosphate deficiency, energy metabolism could no longer function effectively. However, because the diet contains sufficient phosphates, phosphate requirements are usually adequately met.
Diseases and ailments
The organism is dependent on a functioning phosphate metabolism. Both too high phosphate concentrations and too low can lead to serious health problems. When blood phosphate levels are too high, the condition is referred to as hyperphosphatemia. There are both acute and chronic forms of hyperphosphatemia. An acute massive increase in phosphate concentration leads to serious disorders that can even be fatal. The phosphates flowing into the blood bind with calcium ions when a certain concentration is exceeded, thus forming calcium phosphate. In the short term, a dangerous hypocalcemia (undersupply of calcium) occurs. This can lead to vomiting, diarrhea, muscle cramps, cardiac arrhythmias, circulatory collapse and sudden cardiac death. In this situation, rapid assistance in the form of infusion of a physiological saline solution is necessary to accelerate phosphate excretion by the kidneys. Chronic hyperphosphatemia initially causes no symptoms. In the long term, however, precipitation of calcium phosphate leads to calcification of blood vessels and kidneys.The consequences are, for example, heart attacks or strokes. Hyperphosphatemia can be caused by several factors. The acute form is mainly formed by massive phosphate intake or by extensive necrosis of tissue areas. In this case, the decayed tissue releases its entire phosphate supply. Chronic hyperphosphatemia is often produced by decreased renal phosphate excretion in renal insufficiency. Increased parathyroid hormone activity may also result in increased reabsorption of phosphates from residual urine. The same is true in the case of vitamin D intoxication. In this case, too, the phosphate concentration in the blood is too high. In the long term, calcification of the blood vessels takes place. This is why dialysis patients, among others, are at risk of heart attacks and strokes in the long term. In these cases, a low-phosphate diet and the binding of excess phosphates with phosphate binders must be ensured. In contrast to hyperphosphatemia, hypophosphatemia is rare. It develops mainly in the case of an extremely one-sided phosphate-deficient diet. This mostly affects intensive care patients on low-phosphate artificial diets, but also alcoholics. An undersupply of phosphates can also occur when taking phosphate-binding drugs such as acid blockers. Since phosphates are responsible for energy metabolism, the energy supply of the cells is disturbed. The drop in ATP concentration also inhibits the release of oxygen into the blood. In extreme cases, this can lead to the destruction of blood and muscle cells.
