Phosphate is a salt of phosphoric acids.Phosphate is found as an anion primarily in the bones and teeth (85%), but also occurs intracellularly (inside the body cells) and extracellularly (outside the cells) in equal concentrations.Only one percent is found in the extracellular space.Serum phosphate is 85% free, with the remainder protein- or complex-bound. The daily requirement of phosphate is between 0.5 and 0.7 mmol/kg bw/d.It is needed mainly for acid-base and electrolyte (salt)-water balance (regulation of pH), as well as for energy balance and nucleic acid synthesis. Serum levels of phosphate fluctuate throughout the day and are highest in the early morning.
The process
Material needed
- Blood serum (serum should be separated from cells after 2-3 h).
- 24 h collection urine
Preparation of the patient
- Not necessary
Disruptive factors
- Blood cells have a high phosphate content, which adds to the serum phosphate in hemolysis.
Normal values – serum (blood)
| Standard values in mmol/l | |
| Newborn | 1,6-3,1 |
| <1st year of life (LY) | 1,56-2,8 |
| 1ST-6TH LY | 1,3-2,0 |
| 7-13 LJ | 1,0-1,7 |
| > 13. LJ | 0,8-1,5 |
| Women | 0,84-1,45 |
| Men | 0,84-1,45 |
Normal values – urine
| Normal values in mmol/24 h | 16-58 |
Indications
Interpretation
Interpretation of elevated values (in serum; hyperphosphatemia (excess phosphate)).
- Alimentary (dietary)
- Excessive intake of phosphate:
- With food
- When drinking colonic irrigation (before colonoscopy), in patients with limited renal insufficiency (kidney weakness).
- Excessive intake of phosphate:
- Endocrinological causes
- Acromegaly (elevated GH levels) – hormonal disorder caused by increased production of growth hormone after completion of growth.
- Hypervitaminosis D (excessive intake of vitamin D).
- Hypoparathyroidism (hypothyroidism of the parathyroid gland).
- Ketoacidosis
- Lactic acidosis – severe acid-base balance disorder leading to hyperlactacidemia (too much lactate in the blood).
- Milk alkali syndrome – metabolic disorder caused by an excess of calcium.
- Pseudohypoparathyroidism (end organ resistance to parathyroid hormone, PTH).
- Metabolic (metabolic) disorders.
- Acidosis – overacidification of the blood.
- Rapid phosphate administration
- Severe hypermagnesemia (magnesium excess) or hypomagnesemia (magnesium deficiency).
- Diseases
- Extensive trauma (injury) resulting in cellular damage.
- Hemolytic anemia – anemia caused by the destruction of erythrocytes (red blood cells).
- Hyperthermia – overheating of the body.
- Immobilization
- Adrenal insufficiency
- Renal insufficiency (kidney weakness)
- Rhabdomyolysis (dissolution of striated muscle fibers).
- Sarcoidosis (inflammatory systemic disease affecting mainly the lungs, lymph nodes and skin).
- Hepatitis (inflammation of the liver)
- Tuberculosis
- Tumors in the bone (also bone metastases – daughter tumors).
- Medication
- Heparin
- Phosphate-containing laxatives
- Vitamin A/D overdose (due to intoxication).
- Cytostatic drugs,
Interpretation of decreased values (in serum: hypophosphatemia (phosphate deficiency)).
- Alimentary (nutritional)
- Excessive iron intake (high iron concentrations reduce phosphorus bioavailability).
- Excessive intake of calcium (high calcium intake results in complex formation, which can inhibit the absorption of phosphorus)
- Alcoholism
- Malnutrition in the context of parenteral nutrition
- Malabsorption
- Inadequate parenteral nutrition
- Vitamin D deficiency
- Endocrinological causes
- Hyperaldosteronism (primary and secondary) – increase of aldosterone in the blood, which regulates electrolyte (salt)-water balance.
- Hyperparathyroidism (parathyroid hyperfunction), primary.
- Hypovitaminosis D (insufficient intake of vitamin D).
- Metabolic (metabolic) disorders.
- Diseases
- Severe malabsorption
- Amyloidosis – extracellular (“outside the cell”) deposits of amyloids (degradation-resistant proteins) that can lead to cardiomyopathy (heart muscle disease), neuropathy (peripheral nervous system disease), and hepatomegaly (liver enlargement), among other conditions.
- Blast crisis in leukemia (blood cancer).
- Chronic diarrhea (diarrhea)
- Diabetes mellitus
- Familial hypocalciuric hypercalcemia (calcium excess; X-linked or autosomal inheritance) – congenital form of excessive blood calcium levels.
- Genetic hypophosphatemia (phosphate deficiency) such as Dent or Wilson disease.
- Hemolytic uremic syndrome (HUS) – triad of microangiopathic hemolytic anemia (MAHA; form of anemia in which erythrocytes (red blood cells) are destroyed), thrombocytopenia (abnormal reduction in platelets/platelets), and acute kidney injury (AKI); Mostly occurring in children in the context of infections; most common cause of acute renal failure requiring dialysis in childhood.
- Intoxication (poisoning) with lead, cadmium.
- Malignancies (malignant neoplasms)
- Paget’s disease (ostitis deformans) – bone disease that leads to very severe bone remodeling.
- Renal insufficiency (kidney weakness)
- Rickets (bone softening)
- Renal tubular losses:
- Fanconi syndrome (synonyms: Debré-de-Toni-Fanconi syndrome; De-Toni-Fanconi complex, glucose-amino acid diabetes) – inherited dysfunction of the energy balance of the proximal tubule cells of the kidney.
- Oncogenic osteomalacia (tumor-related bone softening).
- Renal tubular acidosis (RTA; acidosis caused by a disturbance in the reabsorption of bicarbonate in the proximal tubule of the kidney).
- Absorption disorders – disorders of absorption of calcium from food, which may be due to malnutrition or vitamin D deficiency, among others.
- Sepsis (“blood poisoning”)
- Condition after partial liver resection (partial liver removal).
- Condition after kidney transplantation
- Condition after parathyroidectomy (parathyroidectomy).
- Medication
- Aluminum-containing antacids (aluminum forms insoluble, non-absorbable compounds with phosphate, so that the absorption of phosphate is inhibited).
- Diuretics (dehydrating agents) such as acetazolamide.
- Hormones
- Proton pump inhibitors (PPI; acid blockers).
- Cytostatic drugs such as cisplatin
- Increased need
- Pregnant and breastfeeding women
Other notes
- The normal requirement for phosphorus is 700 mg/d for women as well as men.
- Phosphate is glomerular (“affecting the glomeruli (of the kidney)”) freely filtered and mostly reabsorbed.
- Reabsorption of phosphate is stimulated by: Phosphate deficiency, IGF-1 and 1,25-(OH)2-vitamin D; excretion is increased by: high phosphate levels, calcitonin, parathyroid hormone (PTH) and glucocorticoids.
