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Inorganic phosphorus in urine
Last reviewed: 04.07.2025
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Reference values (norm) for the excretion of inorganic phosphorus in urine in adults on a diet without restriction are 0.4-1.3 g/day (12.9-42.0 mmol/day).
To diagnose disorders of inorganic phosphorus metabolism in the body, its content in blood serum and urine is simultaneously determined.
Hypophosphaturia is possible with decreased secretion of phosphates in the distal tubules in the case of hypoparathyroidism, parathyroidectomy, with a limitation of the amount of glomerular filtrate, with diseases such as rickets (with a high calcium content in the diet), osteoporosis, a number of infectious diseases, acute yellow atrophy of the liver, acromegaly, with a deficiency of phosphorus in the diet, large losses of phosphorus through the intestine and / or impaired absorption, for example, with enterocolitis. A decrease in the excretion of phosphates in the urine is observed in tuberculosis, febrile conditions, with renal insufficiency.
The mechanisms of increased excretion of phosphates in urine are as follows.
- Phosphaturia of renal origin, caused by impaired reabsorption of phosphorus in the proximal tubules of the kidneys, i.e. in rickets that is not amenable to treatment with vitamin D, after kidney transplantation. Excretion of phosphorus greater than 0.1 g/day in the presence of hypophosphatemia indicates excessive loss by the kidneys.
- Phosphaturia of extrarenal origin caused by primary hyperfunction of the parathyroid glands, malignant bone tumors with increased osteolysis, rickets, with increased cell breakdown (for example, in leukemia).
In rickets, the amount of phosphorus excreted in urine increases 2-10 times compared to the norm. Phosphaturia is most pronounced in the so-called phosphate diabetes. The symptoms of rickets observed in this disease do not respond to vitamin D therapy; massive phosphaturia in this case serves as an important sign for diagnosis.
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