Hypophosphatemia

A decrease of serum inorganic phosphate below the normal range (0.80–1.45 mmol/L or 2.5–4.5 mg/dL), leading to impaired cellular energy production, neuromuscular dysfunction, osteomalacia, and rickets.

Causes

• Reduced phosphate intake

  • Malnutrition

  • Starvation

  • Severe dietary phosphate deficiency

  • Alcohol abuse

• Renal phosphate loss

  • Hyperparathyroidism

  • Cushing syndrome

  • Diuretic therapy

  • Iron infusion–induced phosphate wasting

  • Renal tubular disorders

  • Fanconi syndrome

  • Vitamin D–resistant phosphate wasting disorders

• Gastrointestinal causes

  • Vomiting

  • Diarrhea

  • Vitamin D deficiency causing reduced intestinal phosphate absorption

  • Antacid use containing aluminum or magnesium

  • Malabsorption disorders

• Cellular redistribution causes

  • Refeeding syndrome after prolonged starvation

  • Diabetic ketoacidosis during treatment due to intracellular phosphate shift

  • Respiratory alkalosis causing increased cellular phosphate uptake

• Endocrine and metabolic causes

  • Vitamin D deficiency

  • Increased fibroblast growth factor 23 (FGF23) activity

  • Osteomalacia-related phosphate wasting disorders

• Severe burns

• Sepsis and critical illness

• Genetic phosphate metabolism disorders