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Kidney Diseases

Kidney disease and low vitamin d

02/15/2007

Question:

Can kidney disease cause vitamin d to be low despite supplements? After testing positive for Anti-dsDNA on three occasions over a nine month period, I suddenly developed high blood pressure and protein in my urine. This was shortly after having kidney stones for two weeks.I also recently found out my grandmother died from bilateral kidney stones at 27; two nieces in their twenties have already had kidney stones, and so has my sister (I am 35, my sister is 44)To my knowledge, no males in the family have had stones (we have five brothers) My endocrinologist tested my vitamin d level because of incessant muscle and bone pain and muscle atrophy. It was low, and she had me start supplements.I had already been taking 1000 units for close to 4 months when I had the blood work repeated, and my level had actually DROPPED half a point. In addition, a DEXA scan showed that I have a z-score of -1.5 in my spine and -2.0 in my hip. Could the low BMD, low vitamin d, kidney stones, high blood pressure, and protein loss be connected to kidney disease? According to the formula on kidney.org, my creatinine level of .9 gives me an estimated GFR of 76. My GP has attributed the protein/high blood pressure to being diabetic, but my HbA1c has been very close to normal for a couple years now (around 5.7)The high blood pressure and protein loss didn`t occur until after I started testing positive for Anti-dsDNA, which I understand to be highly specific for lupus, and especially lupus nephritis. I asked my GP for a referral to a nephrologist but he declined, and the local nephrologist I contacted required a referral. I am concerned my continuing low vitamin d may be due my kidneys being unable to convert it to it`s usable form. I`m also concerned that there might be a hereditary or genetic component at work here. Any insight or advice would be greatly appreciated.

Answer:

You appear to have several problems, which may or may not be related.  Protein in the urine can definitely be caused by diabetes, or by hypertension, or by lupus and related diseases.  You are right that the anti-dsDNA antibodies are relatively specific for lupus, but I wonder why your doctor ordered the test in the first place.  Do you have other symptoms or signs of lupus, such as a rash on your face or joint swelling and pain?  Or were other lupus-type tests (such as an ANA, or C3 and C4) positive previously?  The positive anti-dsDNA should definitely be followed up by a nephrologist, as should the protein in your urine.  

The kidney stones may not be related to your other findings.  Oftentimes a tendency to kidney stones does tend to run in families, and it would be interesting to know more about the composition of the stones in your family members, if they have ever been analyzed.  Sometimes there are high levels of calcium or oxalate or uric acid within the stones, and these can be medically treated so that stones will not form (or at least, not as often). 

You do not say which form of vitamin D you were tested for.  A low vitamin D level can be caused by lack of vitamin D in the diet, or by lack of sun exposure.  The conversion of vitamin D (called D3) to its usable form (also known as 1,25-dihydroxy-vitamin D3) is impaired in people with kidney disease, but your renal function appears to be very close to normal.  I would discuss the results with your endocrinologist: ask which form of vitamin D is low in your case, and how she interprets your bone densitometry results.   

Meanwhile, you definitely do need a referral to a nephrologist for your proteinuria, which is of concern with your history of diabetes, hypertension, stones, and the positive anti-dsDNA antibodies. 

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Response by:

Mildred   Lam, MD Mildred Lam, MD
Associate Professor of Medicine
School of Medicine
Case Western Reserve University