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Vitamin D and Chronic Kidney Disease

August 24, 2016

Vitamin D is a common supplement and many people incorporate it in their medical regimen, either at the recommendation of their primary care physician or based on ads seen in the media.

 

Vitamin D comes as Vitamin D2 (ergocalciferol) and Vitamin D3 (cholecalciferol); in the liver they become calcidiol (25-hydroxyvitamin D); the kidneys further transform  calcidiol into Calcitriol (1,25 dihydroxyvitamin D).

 

What is commonly measured in the lab is the calcidiol; a level less than 30 ng/ml is considered low and supplementation is recommended.

 

If you have chronic kidney disease (CKD), vitamin D treatment can be tricky.

 

For mild to moderate CKD – stages 1 through 3, vitamin deficiency is treated the same way as for non - kidney patients.

 

In CKD stage 4 and 5 the kidney’s structure and function is severely compromised; the enzymes in charge of forming calcitriol are usually depleted. The very low calcitriol levels cause the calcium levels to drop and the parathyroid hormone (PTH) levels to rise; clinically this manifests as bone disease and in time it causes bone pains and increases the risk of fractures.

 

If the calcidiol level is also low (less than 30) – supplementation with Vitamin D2 or D3 is recommended. But this will only modestly improve the PTH level and improve the prognosis of the bone health.

 

So once the Calcidiol levels are corrected, treatment with calcitriol or a derivative is recommended to improve the high PTH levels. Once treatment with calcitriol is started, close monitoring of calcium, phosphorus and PTH levels is necessary. There is significant increase in calcium absorption and if the calcium levels are allowed to increase above normal levels they can cause extraskeletal calcifications, mainly vascular, increasing the risk of peripheral vascular disease, heart disease and stroke. Should the calcium level rise too much, the dose can be decreased or the drug stopped for a while.

Commercial formulations of calcitriol and its derivatives are: Rocaltrol, Calcijex, One-Alpha, Zemplar or Hectorol.




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