Hyperphosphatemia

A hyperphosphatemia is defined by a phosphate level greater than 1.45 mmol/l, subject to the reference laboratory's norms. It is rarely encountered and generally asymptomatic.

It most often occurs in expected conditions: renal failure or cellular lysis (extensive necrosis, tumor lysis syndrome). There is a diurnal variation in phosphate levels of up to 0.4 mmol/l (lower values in the morning than at night).

Clinical Presentation

Hyperphosphatemia is generally asymptomatic. However, it may sometimes lead to the progression of chronic kidney disease, secondary hyperparathyroidism and its manifestations (pain, pathological fractures, ...), pruritus, and calcifications (vascular, renal, pulmonary), ...

It should be noted that hyperphosphatemia may be accompanied by hypocalcemia, which should always be checked.

Etiologies

• Increased exogenous phosphate intake:
  • Laxatives, enemas
  • Infusions
• Redistribution from the intracellular to the extracellular compartment:
  • Tumor lysis syndrome
  • rhabdomyolysis
  • Hemolysis
  • Metabolic acidosis
• Impaired elimination (the most common mechanism) and excessive tubular reabsorption:
  • Acute or chronic renal failure
  • Insufficient extraction during dialysis
  • Hyperthyroidism, (pseudo)-hypoparathyroidism, acromegaly
  • Treatment with bisphosphonates, FGFR inhibitors, vitamin D
  • Familial tumoral calcinosis

Therapeutic Management - Treatments

• Etiological treatment if possible, especially useful in cases of excessive exogenous intake
• In cases of cellular lysis: isotonic/alkaline saline infusions
• In cases of significant renal failure:
  • Phosphate-restricted diet (800 mg/day) = limiting protein intake
  • Phosphate binders (CaCO3, ½ to 2 sachets of eucalcic/day, during meals, monitor calcium levels)
  • Consider parathyroidectomy in cases of poorly controlled secondary hyperparathyroidism