What are the causes and effects of hyperphosphatemia in chronic kidney disease (CKD)?

Updated: Oct 26, 2020
  • Author: Pradeep Arora, MD; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Answer

Phosphate retention begins in early CKD; when the GFR falls, less phosphate is filtered and excreted, but because of increased PTH secretion, which increases renal excretion, serum levels do not rise initially. As the GFR falls toward CKD stages 4-5, hyperphosphatemia develops from the inability of the kidneys to excrete the excess dietary intake.

Hyperphosphatemia suppresses the renal hydroxylation of inactive 25-hydroxyvitamin D to calcitriol, so serum calcitriol levels are low when the GFR is less than 30 mL/min/1.73 m². Increased phosphate concentration also affects PTH concentration by its direct affect on the parathyroid glands (posttranscriptional effect).


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