5th April 2024

Hyperphosphatemia

The most common cause of hyperphosphatemia is renal failure as filtration of inorganic phosphate is significantly reduced when the glomerular filtration rate falls < 30 mL/min, increasing the serum phosphate concentration. Other causes include:

• Rhabdomyolysis
• Tumour lysis syndrome 
• Excessive use of phosphate containing laxatives/enemas
• Vitamin D intoxication increasing intestinal phosphate absorption
• Hypoparathyroidism, acromegaly and thyrotoxicosis enhance renal phosphate reabsorption 
• Tumoral calcinosis, which can be genetic or secondary, seen in patients undergoing renal dialysis
• Pseudohypoparathyroidism – characterised by resistance to PTH at its receptor and resultant hyperphosphatemia, hypocalcaemia and raised PTH levels. 

Pseudohyperphosphatemia is a laboratory artefact due to interference in phosphate assay and is sometimes seen in patients with hyperglobulinemia, hyperlipidaemia and hyperbilirubinemia.