Skip to Main Content

Source: Pai, AB. Disorders of Calcium and Phosphorus Homeostasis. In: DiPiro, JT, Talbert RL, Yee GC, Matzke GR, Wells BG, Posey LM. Pharmacotherapy: A Pathophysiologic Approach. 8th ed. Accessed August 20, 2012.

  • Serum phosphorus >4.5 mg/dL (>1.45 mmol/L)

  • Results from renal failure or endogenous intracellular phosphate release.
    • Tumor lysis syndrome in patients treated for leukemia or lymphoma
    • Hemolysis
    • Rhabdomyolysis

  • Impaired glomerular filtration rate (GFR) decreases renal tubular reabsorption, leading to phosphate retention.
    • Under normal conditions, 85–90% of filtered phosphate reabsorbed via proximal tubule.
    • Retention of phosphate decreases vitamin D synthesis and induces hypocalcemia, leading to increase in parathyroid hormone (PTH).
  • Administration of oral and rectal phosphate-containing solutions in patients with moderate to several renal insufficiency can result in hyperphosphatemia.

  • Rare in general population.
  • Incidence: 70% in renal insufficiency or renal failure.
    • Nearly universal finding in patients with stages 4 and 5 chronic kidney disease (CKD).

  • Acute or chronic renal failure
  • Chemotherapy administration for leukemia or lymphoma

  • Uncommon in patients with normal kidney function.
  • May present as hypocalcemia and tetany.

Signs and Symptoms

  • Acute symptoms include:
    • Gastrointestinal (GI) disturbances
    • Lethargy
    • Obstruction of urinary tract
    • Seizures (rare)
  • Chronic hyperphosphatemia associated with deposition of calcium-phosphate crystals into soft tissues, intrarenal calcification, nephrolithiasis, or obstructive uropathy.
    • Likely to form when product of serum calcium and phosphate concentrations exceeds 50–60 mg2/dL2 (44.8 mmol2/L2).
    • Calciphylaxis: tissue necrosis resulting from precipitation of crystals in arteries, joints, soft tissues, and viscera.

Means of Confirmation and Diagnosis

  • Serum phosphorus >4.5 mg/dL (>1.45 mmol/L)

Laboratory Tests

  • Metabolic panel
    • Serum phosphorus
    • Serum calcium
  • Parathyroid hormone
  • Vitamin D level

Differential Diagnosis

  • Normalize serum phosphate concentrations (or near normal in CKD).
  • Minimize long-term cardiovascular consequences of calcium-phosphate crystal deposition

  • Most effective way to treat nonemergent hyperphosphatemia: decrease phosphate absorption from GI tract with phosphate binders.
  • Severe symptomatic hyperphosphatemia manifesting as hypocalcemia and tetany treated by IV administration of calcium salts.

  • Evaluate serum calcium every 4–6 hours during IV calcium infusions.

  • Increased morbidity and mortality with serum phosphate concentration >6.5 mg/dL (2.10 mmol/L)

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.