Inorganic phosphorus in the blood

Phosphorus in the body is contained in the inorganic (calcium, magnesium, potassium and sodium phosphates) and organic (carbohydrates, lipids, nucleic acids, etc.) compounds. Phosphorus is necessary for the formation of bones and cellular energy metabolism. Approximately 85% of all phosphorus in the body is in the bones, most of the rest is inside the cells, and only 1% is in the extracellular fluid. Phosphates are the main intracellular anion. In the cellular elements of blood, phosphorus is present only in the composition of organic compounds, and serum contains mainly inorganic phosphates, the determination of which is of the greatest interest to the clinician.

In addition to inorganic phosphorus, whose concentration in the serum and erythrocytes is almost the same, the fraction of acid-soluble phosphorus and lipid phosphorus is also differentiated in the blood. Approximately two-thirds of the total acid-soluble phosphorus of the blood is a part of 2,3-diphosphoglyceric acid, the amount of which increases with all diseases accompanied by hypoxia; the rest is represented by phosphorus ATP and ADP. Most of the lipid phosphorus accounts for the proportion of phosphatidylcholines (lecithins) and phosphatidylethanolamines (cephalins). Approximately 40% of phosphorus not used by the body is excreted with feces, and the rest - with urine.

Reference values (norm) of concentration of inorganic phosphorus in blood serum

Age	Concentration of phosphorus in blood serum
	Mg / dL	Mmol / l
24-48 h	5.5-9.5	1.78-3.07
Up to 1 year	4.5-6.5	1.45-2.10
Children	4.5-5.5	1.45-1.78
Adults	2.7-4.5	0.87-1.45
Older than 60 years:
Men	2,3-3,7	0.74-1.20
Women	2.8-4.1	0.90-1.32

The role of phosphorus compounds is that they serve as a plastic material, participate in the regulation of CBS and in various processes of metabolism of carbohydrates, fats and proteins. Phosphorus is involved in the formation of nucleic acids, nucleotides, phospholipids and other compounds. The concentration of phosphorus below 0.3 mmol / l leads to a disruption in the energy metabolism of cells.

The main factors regulating phosphorus metabolism are PTH, which reduces the concentration of phosphorus in the serum by activating its excretion by the kidneys; 1,25-dihydroxycholecalciferol, which increases it by activating the absorption of phosphate in the intestine; calcitonin, which has a hypophosphatemic effect; insulin, which reduces the concentration of phosphorus by stimulating its transfer into cells. The exchange of phosphorus in the body is closely connected with the exchange of calcium, so the quantitative ratio of calcium and inorganic phosphorus in the blood is of great diagnostic importance. Normally, this ratio in children is 1.9-2, and when rachitis rises to 3 or more.

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