Phosphorus
Overview
Phosphorus, measured as inorganic phosphate in serum, is an essential mineral critical for bone mineralization, energy metabolism via ATP, and cellular signaling. It exists primarily as phosphate ions and is tightly regulated by kidneys, parathyroid hormone, and vitamin D. Elevated levels (hyperphosphatemia) may indicate kidney dysfunction, hypoparathyroidism, or tissue damage, while low levels (hypophosphatemia) suggest malnutrition, hyperparathyroidism, or renal phosphate wasting; it is clinically useful for assessing electrolyte balance, chronic kidney disease progression, and bone health disorders .
Clinical Use Cases
- Monitoring chronic kidney disease and dialysis adequacy.
- Evaluating parathyroid function and calcium-phosphate metabolism.
- Diagnosing hypophosphatemia in critical illness or refeeding syndrome.
- Assessing bone disorders like osteomalacia or rickets.
- Guiding nutritional support in malnutrition or alcoholism.
Specimen Types
- Serum.
- Plasma.
- Whole blood (heparinized).
Measurement Methods
- Colorimetric assays (phosphomolybdate method).
- Automated analyzers in clinical labs.
- Ion-selective electrodes (indirect).
Test Preparation and Influencing Factors
- No fasting required, but recent meals can transiently elevate levels.
- Avoid hemolysis, as it falsely increases results.
- Influenced by vitamin D supplements, phosphate binders, or laxatives.
- Diurnal variation and age-related changes (higher in children).
- Acid-base status or insulin therapy affects levels.
Synonyms
- Serum phosphate.
- Inorganic phosphorus.
- Phosphate (PO4).