Monday, June 14, 2010

Bone pain: Lessons learnt

There is a very important lesson to be learnt from the bone pain saga of the last eight months or so.

Nocturnal dialysis is a very different ball game compared to conventional thrice a week in center dialysis. PTH levels are a very important factor for people on dialysis. A lot of dialyzors have something called secondary hyperparathyroidism which is basically an abnormally high parathyroid hormone level in the blood. The body regulates the Calcium level in the blood by secreting this hormone from the parathyroid glands. In people on dialysis, this mechanism of Calcium contol is disturbed and the body starts secreting excess parathyroid hormone.

In nocturnal dialysis, this system is affected by an extra factor. The dialysate. The blood is in contact with the dialysate for about seven to eight hours every day. This is almost a third of the day. This can have a great effect. What happens is that the contents of the dialysate affect the composition of the blood. Excess calcium, for example, in the dialysate can move into the blood. Less calcium in the dialysate can cause calcium to be pulled off from the blood. The body also keeps calcium balanced between the blood and other parts of the body, notably the bones.

The cause for the bone pain was the extremely low calcium in my acid cans which forms my dialysate.

Now coming to the solution. The key to getting all the lost calcium into my bones was increasing the absorption of calcium from the food into the blood and subsequently into the bones. This is achieved by Vitamin D. So, I would need to take Vitamin D supplements. The supplement of choice in most dialyzors is calcitriol which is the active form of Vitamin D, the form that is used directly by the body. The problem with calcitriol is that it suppresses PTH. And a low PTH causes another set of problems - Adynamic Bone Disease being the most common.

That however was not the case with me. I was on a relatively high dose of calcitriol with no suppression of PTH. The reason behind this was the long exposure to the Calcium in the dialysate. The PTH is inversely proportional to the amount of Calcium in the blood. So, the dialysate Calcium was affecting the blood Calcium which in turn was affecting the PTH. This effect was much greater than any suppression caused by the Vitamin D.

This would not usually be the case with conventional dialysis where the exposure to Calcium in the dialysate is much, much less due to the short duration and lesser frequency of dialysis.

The thing with nocturnal dialysis is that it is relatively new and there are very few people on this modality. As a result, a lot of the decisions have to be made by the doctors more out of common sense than by relying on any systematic and published studies.

3 comments:

Madras Hash said...

Can others learn lessons too? For instance, I see many people, especially menopausal women, taking calcium supplements. This is to ensure that their bones do not get brittle as they age as calcium leaches out. Most of the calcium they take is not absorbed, so they take mega doses.

Would Vit-D help them in calcium absorption, in which case it should be included in all calcium supplements, and people can take smaller doses.

Related question:
Do we in India, with so much sunlight need to take Vit-D supplements? I learnt in school that exposure to sunlight was enough to ensure adequate Vit-D in the body.

Kamal D Shah said...

People with kidney failure are very different from people with healthy kidneys. One very important function of the kidneys is to convert the inactive form of Vitamin D (the one that is absorbed from sunlight) and convert it to the active form, which is calcitriol and is eventually used by the body to absorb Calcium.

For people with healthy kidneys, sunlight is usually enough (unless they rarely venture outdoors) and the kidneys convert this inactive form into calcitriol.

When the kidneys don't function, you need Calcitriol supplements directly because no matter how much inactive Vit D you get from the sunlight, it is not going to be converted to Calcitiol which is eventually what is used.

So, to answer your question, healthy people should get their inactive Vit D level tested and they will need am inactive Vit D supplement (Calciriol granules) and that might help them. But they will never need Calcitriol supplements.

GOLDEN TRAILS said...

Kamal Shah, good to read about your experience as well as to note there are still genuine doctors around! Vitamin D is not exactly a vitamin, its more of a hormone and has direct relevance to over 2000 genes in our body. For more on this do go through this informative article "Vitamin D3 or Disease, Disability & Death" posted in blog GOLDEN TRAILS - http://vishigan.blogspot.com/2012/01/vitamin-d3-or-disease-disability-and.html. Good luck!