Test Findings
 

Hypophosphataemia

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Overview

  • Hypophosphataemia refers to a reduced serum phosphate concentration of <0.8 mmol/L. This may occur in the context of reduced intake, compartmental shift or increased excretion of phosphate.

Aetiology

    • Causes of Hypophosphataemia

    • Reduced Intake / Uptake

    • Severe malnutrition - starvation, alcoholism, anorexia, TPN
    • Malabsorption
    • Vitamin D deficiency
    • Phosphate binders (CKD patients)
    • Antacids
    • Compartmental shift

    • Insulin - recovery post DKA, refeeding syndrome, insulin infusion, glucose infusion
    • Severe respiratory alkalosis
    • Hungry bone syndrome
    • Increased excretion

    • Hyperparathyroidism
    • Vitamin D deficiency
    • Diuretics - acetazolamide, thiazides, loop diuretics
    • Osmotic diuresis (e.g. poorly controlled diabetes)
    • Iron infusion
    • Post renal transplant
    • Fanconi syndrome

Approach

    • Signs and Symptoms

      Generally asymptomatic except for in severe hypophosphataemia.
    • Anorexia
    • Lethargy
    • Muscle weakness
    • Seizures
    • Coma
  • If the cause is not apparent, urinary phosphate (either 24-hour urine or fractional excretion) may be useful in differentiating increased excretion from other causes.
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