Palaniappan
Forum Senior
Topics: 30
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Please let me know whether the following sequence is correct???
Chronic Renal failure--->Decreased Vitamin-D---->Decreased calcium--->increased PTH--->1.Bone resorption
2.Decreased Phosphate level in the blood due to PTH action on renal tubles of increasing po4 excretion
I was faced with a question which had botht he above answers in the options and the correct answer was Bone resorption-Osteitis fibrosis cystica..I am not sure why hypophosphatemia(the other option) is not correct??Could anyone throw some light on this aspect??
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| Ancylostoma
Forum Guru
Topics: 42
Posts: 642
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The failure of kidney causes the loss of calcium and retention of phosphate. In secondary hyperparathyroism you have a increase po4 level, increase in pth, but a decrease in calcium.
Edited by Ancylostoma on 12/23/06 - 10:57 PM
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| Ancylostoma
Forum Guru
Topics: 42
Posts: 642
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Lets clarify the answer, with renal failure you have loss of the ability to for 1,25 oh cholecaciferol (calcitriol). Calcitriol is normally require to increase the absorbtion of ca and phosporus in the kidney and intestinal cells. So we have a decrease in ca. You would think that this would mean we have a decrease phosphate too. It doesn't because the failure of the kidney prevents the kidney from secreting phophate(somthing it does normally) and thus we have a elevated phosphate . So in summary 2ndary hyperparathyroism via the kidney failure, high pth, low ca, high phophate
Now if the 2ndary hyperparathyroidism is via low dietary intake of vitamin d, you have a high pth , low ca, and low phosphate (lack of reabsortion via calcitriol).
Finallly if we have a high pth , low ca , high phosphate , in the absence of renal failure. You must consider psuedohypoparathyoism(PTH resistance). In this case PTH induction will fail to cause a increase in urinary camp. I hope this add some clarity to your problem
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| Palaniappan
Forum Senior
Topics: 30
Posts: 148
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Thanx bro:-)
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