Phosphate

Normal range ~ 1mmol/l

• regulated with calcium
• body content 20mol (600g)
• RDA about 800 mg (80% absorbed)
• Lost in faeces and urine (15-50 mmol/day)

Functions

• membrane structure
• high energy bonds (e.g. ATP)
• nucleic acids
• bone structure (as hydroxyapatite)
• intermediates
  • glycolysis
  • proteins
• buffer (H₂PO4)

Controls

• 1,25 dihydroxy-vitamin D₃ (calcitriol)
  • Decreased serum phosphate increases 1,25-(OH)₂-D
    • increases uptake of phosphate from gut
    • excess calcium excreted in urine

Also affected by

• Parathyroid hormone (PTH)
  • increases release from bone
  • increases uptake from gut
  • increases renal excretion

Disorders

• Hyperphosphataemia
• Hypophosphataemia

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