Vitamin D, Calcium, and Phosphate

[tincan]

My patient had high serum phosphate level and low serum vitamin D level, and it didn't quite make sense to me...

I know that Calcium and Phosphate level has an inverse relationship (something to do with the kidneys)...

When I look up Phosphate on a lab values text, it says that for an INCREASE of phosphate, the cause might be due to an EXCESSIVE AMOUNT OF VITAMIN D LEVEL. What the textbook said to me made sense because I thought it should be something like...

High vitamin D --> More calcium absorption into bones --> low serum calcium level --> high serum phosphate level (due to the inverse relationship, and phosphate being released form bone by vitamin D)

So it didn't made sense to my why my patient would have low serum vitamin D level AND high phosphate level. Can someone please help me out here? Thanks.

The possible cause of low vitamin D level could be because this patient has been hospitalized for 2 months and not getting much sunlight.

[Cupcake89121]

Could it be that the imbalance is actual and not relative? I could be totally wrong and have no idea what I'm talking about; I'm just a soon-to-be 3rd semester nursing student. That is the best "studying for MedSurg final at 6am on a Friday morning" answer that I could come up with right now. Hopefully one of the more experienced/knowledgeable students and/or nurses will jump in. :)

[Soliloquy, MSN, APRN, NP]

Hey tincan! You're getting me to think and do research! I like this. :)

If you patient has a kidney issue, think of it like this: The patient's kidneys aren't functioning so the kidneys aren't converting vitamin D to it's active form which culd explain the reading of low Vit D. What's then happening is that the phosphate is then being removed from the body via the urine and that gives the high reading of phosphate. You get it? So because your patient doesn't have enough Vitamin D, whatever phosphate the patient is getting from their diet is simply being excreted as opposed to absorbed and used in the body.

Here's the link: http://www.kidney.org.uk/Medical-Info/Calcium-Phosphate/#7

What can go wrong with Calcium, Phosphate, PTH and Vitamin D in Kidney Failure?

If someone developed kidney failure and went onto dialysis, the following sequence of events might occur. However, preventative treatment can stop many of these problems.

A fall in the blood level of calcium is the first major change. As the kidneys do not convert vitamin D into its active form, calcium does not get into the body from food, and the blood level of calcium can fall. The treatment is to replace active vitamin D (more details above).

Levels of phosphate in the blood rise, because the kidneys are not excreting excess phosphate into the urine. High levels of phosphate can cause itching. The treatment is to reduce phosphate levels by diet, dialysis, and medication (more details below).

PTH may be produced in large quantities, stimulated by low levels of calcium in the blood. The PTH tries to keep the calcium level in the blood normal by increasing calcium absorption from food, but also takes calcium out of the bones. Eventually the parathyroid glands work so hard they go out of control, and cause persistently high calcium levels. This may require an operation to remove the glands (the operation is called a parathyroidectomy, more details below).

[Mythteary]

Options:

Diet, environment, body organs, medical conditions.

After most of these are considered,

in diet most people forget that certain types of phosphate salts are used in food products for different purposes. Such as smoothing, thickening, mixing, even preservation. Check the diet first for obvious over phosphorusing, then check the foods additives in the fine print.