Bone health

Dear Dr. Agar,

My questions are:

  1. Do nocturnal length txs improve bone health…should one doing nocturnal txs begin to notice any changes in the PTH, cal., phos balance and other bone issues for the better?

  2. Does adjusting the hrs of tx to lets say from 8 hrs to 7 hrs have any affect on the PTH, cal, phos balance?

  3. Also, I would like to know if in Australia, measurement of the PTH “ratio”, along with PTH, is done as it is done by Scantibodies Labs in the U.S. for supposedly more accurate measurement of PTH? I find their website very informative. Our clinic uses their method, but I don’t know any other patients whose nephs use Scantibodies. Not sure if Scantibodies is something we just have here in the U.S or if other countries have something similar.

I know, I know, I’m looking at the #s again, but I really do think like you, Dr. Agar, in that I believe dialysis should be individualized to the patient. If you had ever read any of my posts on this site you would know I have long advocated individualization/optimization and had attempted to get nocturnal txs for years before finally being given the opportunity about a year ago. This girl believes in optimal dialysis whatever that takes and I very much believe in starting with the best so it is possible to look at the big picture overall rather than having to focus on the #s. Unfortunately, that’s not how dialysis has been typically done in the U.S. With barely adequate txs being the norm here for most of the patient population, is it any wonder we have been programmed to look at the #s ?!? I am most glad to be turning things around with my txs for the first time. THAT is a good feeling!

1) Do nocturnal length txs improve bone health…should one doing nocturnal txs begin to notice any changes in the PTH, cal., phos balance and other bone issues for the better

There is conflicting evidence regarding the effect of NHD on bone. Early on in NHD – and this was our experience too – the Canadian team(s) found a sharp fall in bone mass density (BMD). BMD is not, mind you, a particularly accurate way of assessing bone … but all/any of the method(s) available to us to measure bone metabolism are still very blunt and are, at best a very inaccurate science. Furthermore, dialysis patients are, in my experience, never very keen to enter studies that use bone biopsies - a fact neither surprising nor unexpected … and nor can I blame them.

It was soon realized that to sustain a positive calcium balance and to improve calcium uptake from bone, a higher than usual dialysate calcium was needed in order that calcium could be moved ‘in’ rather than ‘out’ across the dialyser membrane. For most (not all) NHD patients in our program, we found that a dialysate calcium of between 1.5 and 1.75mmol/L seemed to be about right … so much so that Fresenius (Australia) now make a special NHD dialysate for us with a 1.6mmol/L calcium concentration – an amount we think is, for us, pretty much where it should be. There has also been debate (unsolved as yet) whether Vit D should or should not be given - and if so, in which form and how much - as PTH falls without calcitriol (or paracalcitrol). PO4 is also so well controlled that in the more frequent forms of NHD, PO4 must be given back via the dialysate and, in addition, as the calcium x phosphate product is so low, some mild low-level hypercalcaemia at the end of dialysis might not only be on no consequence but actually be seen as an advantage. We like to see our pre-dialysis Ca++ levels at ~2.40mmol/L - and this will rise such that, by the end of dialysis, the Ca++ is ~2.60-2.65mmol/L as the PO4 levels fall from a mean pre-dialysis level of ~1.35-1.45mmol/L to ~0.65-0.75 mmol/L by the end of dialysis - the calcium phosphate product throughout being commonly <3. Is this the right approach? Will bone benefit or not? In truth, no-one knows. It seems to be the right approach - to us. We think bone will benefit. But, do we know? … no, in truth, we don’t. Sadly, patients sometimes expect too much of us … or too often think (or expect) all the answers to be known. They aren’t. We can only do what we think is best. We must try to keep an open mind and learn along the way.

Jane, put simply - we still just dont know enough about all this - nor what is right, or right for most. And, as for ‘noticing changes’ … we dont even know (or agree on) what changes we should notice. We can’t agree how best to measure - your later question (Part 3) about the way to measure PTH is just such one case in point.

Bone metabolism in dialysis patients is a debated, uncertain and still largely unknown or poorly understood area (indeed, one of the most debated, the least known) - and all the wishing will not and does not change that. I suspect it will be thus for many years yet. It will be a long time before we really understand what happens to bone in renal failure or how our treatments (long, short, frequent, infrequent) influence it - either for the good or for the bad - and what exactly we should do, one way or the other. It is an area where there are more questions than answers - and much of what you have asked is just not known … there are hot opinions, yes, but facts - few! Hot opinion does not equal knowledge … and knowledge, we lack.

As all of this information (and debate) is in the medical literature and is still medically neither solved nor agreed, I think any ‘additional’ discussion is probably beyond the scope or need of most patients who read these pages.

2) Does adjusting the hrs of (treatments) to lets say from 8hrs to 7 hrs have any affect the PTH, cal, phos balance?

No … I doubt it … certainly not an effect that could be demonstrated nor one of likely clinical significance. Our current assessment techniques of bone metabolism are blunt, at best, and no statistical difference would be able to be shown with such a minor change.

3) Also, I would like to know if in Australia, measurement of the PTH “ratio”, along with PTH, is done as it is done by Scantibodies Labs in the U.S. for supposedly more accurate measurement of PTH? I find their website very informative. Our clinic uses their method, but I don’t know any other patients whose nephs use Scantibodies. Not sure if Scantibodies is something we just have here in the U.S or if other countries have something similar.

No. we do not, clinically, use the Scantibody assay. The majority (if not all) papers on this issue seem to suggest that there is little or no advantage. Again, you will no doubt be able to quote some who would disagree with me but most of the information I have seen on this subject is summed up (here paraphrased) by a UK group from Nottingham (Godber IM, Parker CR, Lawson L et al: Annals of Clinical Biochemistry) who concluded … “the ‘whole molecule’ PTH assay (ie: the "Scantibodies” assay) is unable to discriminate and provides very little additional clinical information to that obtained from the intact PTH assays”.

I suspect their general conclusion underlines why, to my understanding, the ‘ratio’ process is not widely used. Again, it may be in the US and if it is, this maybe a US-centric phenomenon … though I am unable to comment of the % of laboratories in the US who do or do not use the Scantibody process. It is probably too narrow a discussion to follow further with here.

John Agar

Thanks so much for this thread, Jane and thanks so much for your response Dr. Agar. I have been struggling with severe bone pain for the last 2 months. I have had a very low phosphorus ever since I switched to daily nocturnal. No amount of oral phosphorus supplementation helped. I also tried adding a phosphate enema to the dialysate but stopped after about a week for other reasons. My PTH was very high at one point. I started cinacalcet for this and it came under control. My active Vit D was very low for which I started calcitriol about 2 months back. PTH is now normal (179). My inactive Vit D level is normal.

The bone pain however continues to get worse with every passing day. I am unable to walk properly. Even turning from one side to another on the bed while lying down is painful. The bone pain is in my back, my ribs and my feet. Any strain on any of these areas causes pain. There is no pain if I am just sitting still or lying still. Any movement that causes these areas to get some strain causes pain.

We have done the DEXA scan, several X Rays, an isotope bone scan and even a Serum protein electrophoresis. All of these have been normal or did not show anything other than secondary hyper parathyroidism (isotope bone scan showed this). My nephrologist has no other ideas about what the cause could be.

I am using a low Calcium dialysate and this is due to my Calcium becoming high about 2 years back. My Calcium is currently 7.5 mg/dl pre dialysis and 8.4 mg/dl post dialysis which after reading your response above I realize is lower than what it should be. My nephrologist has suggested switching to a regular Ca dialysate and I am doing that immediately.

Currently the bone pain is my biggest problem and I am really at a loss about what I could do. It is affecting my life in a very negative way as merely going about my daily activities has become difficult. Dr. Agar, do you have any suggestions on what the problem might be?


I think I may have hit upon the reason for my bone pain!

Around October 2007, my Calcium went high - about 11.7 mg/dl (normal 8.5 to 10.5 mg/dl). At that point my nephrologist asked me to stop taking Calcitriol and asked me to switch to a low Ca dialysate. The normal dialysate here has 3 meq/l of Calcium. He asked me to switch to one with 2.25 meq/l. I did that. Initially I used to check the label on the Acid can and it was right. I checked the label on the acid can a few minutes back. Guess what - it is only 1.5 meq/l !!! I don’t know when they started supplying these extremely low Calcium acid cans! This is far lower than what I had wanted.

I have not been checking the label from many months. I somehow feel that this is the reason for my bone pain. Too much calcium being pulled out from my blood and consequently from the bones. I am ordering a batch of normal Calcium acid cans immediately and will be switching to that from tonight.

I really hope my reasoning is correct!


Dear Kamal

I am not surprised you have bone pain … and I think the problem is your calcium! As you say, your PO4 levels are in your boots but so are your calcium levels. No wonder your PTH is so high and, even though it has ‘responded’ to Cinacalcet, from what I can deduce from what you have told me, I think you need calcium … and a truckload of it.

You say you have had a Dexa scan but I don’t know your Z scores which, my guess is, would be minus – and lots minus too.

In my SI unit language, I have your pre- and post- calcium levels ranging 1.87 – 2.09 (that is if I understood the meaning of the numbers you gave – 7.5 – 8.4 - and if my conversion tables are right and the conversion = mg/dl x 0.2495). I would suggest that you need a bath (dialysate) calcium of 1.75 mmol/l and lots more calcitriol than your current dose too.

Admittedly, advising like this has lots and lots of traps and I neither know you nor your other circumstances but certainly, on the face of it, you are likely decalcifying bone at a great rate. No wonder you hurt ++++. You need to have that looked at – and quickly.

You will need to have your calcium levels monitored quite closely but that, I think, is the answer. I am not at all surprised you are in pain. It can be reversed but it needs hands on and careful monitoring. I think (and I know Andreas Pierratos thinks similarly) that when the phosphate is so low (as it is in frequent and overnight NHD), that modest post-dialysis hypercalcaemia is OK … up to a Ca++ blood level post-dialysis of 2.7mmol/L or even up to 2.75mmol/L (provided the PO4 is low - which it is). That is probably, at least in the short term, where you should be aiming your post Ca++, at least until your pains settle … and that may take a while as I suspect the rate of Ca++ leeching form bone has been quite high … then, maybe, it would be time to drop the posts back to a 2.6 range thereafter.

As your PO4 is low (and in you, it seems to have been very low), I still think you will need PO4 supplementation in some format and as your CaxPO4 product is low, the risk of extra-osseous calcification (like calcifying your blood vessels) is also low … if any risk is there at all (which I suspect there isnt). Pierratos has shown resorption of extraosseous calcification on NHD with high dialysate Ca++ concentration but a low phosphate and a low CaxPO4 product.

Go get some calcium!

John Agar

Thanks so much Dr. Agar for your explanation. It all makes sense now! I am going to switch to the 1.75 mmol/l Ca acid right away.


Just wanted to post a quick update - after 4 days of using regular Calcium dialysate (3 mEq/l) and one day of nigh Calcium dialysate (3.5 mEq/l) - I got only 5 days of dialysis last week, was on a holiday - my Calcium is now 10.7 mg/dl or 2.675 mmol/l. My Phosphorus is at 1.7 mg/dl or 0.548 mmol/l. I had also doubled my dose of Calcitriol to 0.5 mcg/day from 0.25 mcg/day.

My Phosphorus has fallen a little. I have been adding the phosphate solution (100 ml) to each can for more than a month. Last week, pre dialysis Phosphorus was 4 mg/dl or 1.29 mmol/l. I wonder why it has fallen.

Dr. Agar, I just thought I would post the update here for you when you returned!


My post dialysis Calcium is 13.0 mg/dl (3.250 mmol/l) and post dialysis Phosphorus is 1.4 mg/dl (0.45 mmol/l). The Ca-P product is 1.46.
My pre dialysis Calcium is 10.7 mg/dl (2.675 mmol/l) and pre dialysis Phosphorus is 1.7 mg/dl (0.55 mmol/l). The Ca-P product is 1.47.

I guess the Calcium is way too high. This is after using a Calcium solution of 1.75 mmol/L for 2 nights. The second night is when these tests were done.

The best part is my bone pain is starting to get better - I would say about 10% after only a week of changing the acid cans to normal or high (high for the last 2 nights).

My question to you Dr. Agar (when you return from vacation) is how long would you say is it ok to have this high a Calcium without running into the risk of extra osseous calcification? I am checking my values every week.

Thanks so much for your help Dr. Agar! I couldn’t have gone this far without you!


One more update:

After another week of regular Calcium dialysate (1.5 mmol/l of Ca) and 0.25 mcg/day of calcitriol in addition to 30 mg of cinacalcet every other day, my PTH has plummeted to 4.7 pg/ml (normal 7 to 53)!! This had at one point reached 1015! I think this proves that the low Calcium was the root of all the problems. I am stopping my cinacalcet completely and am continuing to use regular Calcium dialysate (3 mEq/l or 1.5 mmol/l) and continuing to use 0.25 mcg/day of calcitriol. I am not sure if I should continue the Calcitriol because that will further cause the PTH to go down. My calcium is currently 10.5 mg/dl (2.625 mmol/l). As always I am discussing all this with my nephrologist. But your thoughts on this would be greatly appreciated, both by my nephrologist and me because there is very little (no? ) experience of nocturnal dialysis available here.



I am not really back from leave till next Monday but have taken 2 days out of my holiday to go to the 3rd Australian and New Zealand Home Therapies workshop in Brisbane ( for any who want to check the program) and I thought I’d drop you a line.

Yes … I would back off the calcitriol entirely for the moment till your PTH drifts up a little though later, when it recovers to about the 15-20 range, a smidge of calcitriol should begin again, I think, though this needs to be run by your nephrologist and monitored by him/her.

Is the bone pain any better?

John Agar

Thanks so much Dr. Agar for your reply! I really appreciate your taking the time in the middle of your vacation to do this!

I have stopped my calcitriol and switched to a regular Ca dialysate (1.5 mmol/l). I plan to check Ca and PTH tomorrow (after a week of the changes).

My bone pain is just about slightly better.

Thanks again Dr. Agar!


Dear Kamal … just interested to know if things are improving - especially the pain - though I know it might take some time. Have you had a recent bone mass density done?

John Agar

Hello Doctor,

Yes, there is some improvement in the bone pain - I won’t say a whole lot, but it definitely is better. I haven’t had a bone mass density test done recently. Is this the same as a DEXA scan? I had this done before I figured out the low Calcium acid can problem. It had some negative T scores but I was told these were not significant.


Hello Doctor,

Yes, there is some improvement in the bone pain - I won’t say a whole lot, but it definitely is better. I haven’t had a bone mass density test done recently. Is this the same as a DEXA scan? I had this done before I figured out the low Calcium acid can problem. It had some negative T scores but I was told these were not significant.


Another question I had Dr. Agar was on the drawing of blood for Serum Phosphorus to be measured. The post dialysis value of Serum Phosphorus is what is important for me. When should blood for this be drawn? Can it be done immediately after dialysis - in fact I am getting the blood drawn from the arterial buttonhole needle before removing it (without any saline inserted). Is it true that phosphorus usually rises and it is best that it is measured a couple of hours after dialysis.

I have been struggling with trying to maintain a normal Phosphorus. I have been adding 100 ml of an enema similar to Fleet to a can of 20 liters of acid. My post dialysis Phosphorus is still around 1.2 mg/dl (0.387 mmol/l). I am wondering if I should wait a couple of hours post dialysis to get a more accurate reading?


Phosphate rebound IS rapid. We do take blood (like you do) before needle withdrawal, recognising that within a short time, the serum PO4 will rise through equilibration (… maybe within 30 mins or so). I wouldnt be too anxious about it … especially if your predialysis PO4 is towards the upper end of the normal range. I am not sure why your post-PO4 is so low … can you remind me of your pre-PO4 again?

You say there is no saline in the line but I still cant help thinking it maybe dilutional. You really do have to be certain that the line HAS been cleared of residual saline.

Have you, for example, had other post dialysis things measured - like the K+ or the Hb? This would be a way of seeing if the ‘lowness’ is PO4-specific or whether (if dilutional) all parameters are low. That would prove the point - one way or the other! If you can be bothered to have another PO4 done 2 hrs post, and it was in the 0.75+ range, it would put your mind at rest and stop you worrying too much.

If it is, however, truly low … and if dilution is excluded by your other post-dialysis measurements being OK … then I am a bit foxed - unless, that is, there is something in your other meds etc I am unaware of.

John Agar

Thanks Dr. Agar for your thoughts.

My pre dialysis phosphorus is around 0.55 mmol/l. I draw the blood from the arterial line, so there is no saline in it. I draw the blood and then push saline into the line.

I will however check the Phosphorus immediately after dialysis and after two hours, as you suggest.


Hello Dr. Agar,

I checked my phosphorus immediately after dialysis and about 2 hours after dialysis and here are the results:

Immediately after dialysis: 1.3 mg/dl (0.419 mmol/l)
Two hours after dialysis: 0.8 mg/dl (0.258 mmol/l)

My PTH immediately after dialysis is 5.3 pg/ml (normal is > 7 pg/ml) and Calcium is 10.9 mg/dl (2.72 mmol/l).

What I am unable to understand is why the phosphorus dropped 2 hours after dialysis.

Also, I have read that too low a PTH can cause adynamic bone disease. What can be done to increase my PTH?

I am currently also adding about 150 ml of phosphate enema to a can of 20 liters of acid. That does not seem to be helping the phosphorus.

Any thoughts on this dear doctor would be really appreciated. My nephrologist and I are both perplexed about this whole issue.


Dear Kamal

The low phosphate of 0.419 immediately post dialysis is, I agree, very low …most of our patients ‘bottom out’ at about 0.65 post NHHD and, remember, the PO4 does usually pop up again fairly promptly in the couple of hours post dialysis. It makes me wonder why your 2 hr post dialysis PO4 actually falls further to 0.258 … I fnd that very odd and inexplicable - unless there is some sampling or measurement gremlin.

Is your lab close? … or is it at a distance where the transport of your blood specimen is needed?

It might also be worth checking that you are using the right tube to collect your blood. EDTA, a substance added to some specimen tubes - or citrate anticoagulants - both can cause a ‘spurious’ or ‘pseudo’ low phosphate. Make sure that the sample tube isnt one that has EDTA in it. That can be a simple but not all that unusual error, particulraly in home-sampled bloods.

As for the low PTH … yes, a low PTH is a laboratory indicator (in dialysis patients) of over-suppression of PTH (I never know how many 'p’s and 's’s to put in suppression!).

So … lets talk bone ‘turnover’ … and by that I mean that just like other tissues and other ‘systems’ in the body, bone is in a constant state of flux … new bone is being made (or laid down) while old bone is being reabsorbed (or replaced).

Bone turnover, the balance between loss and renewal, is the phrase some use to describe this state of flux.

Another example of dynamic flux is in red blood cell ‘balance’ where old red cells are constantly being replaced by new, the old ones being chewed up by the spleen (in particular) and their iron recycled into the new red cells that are being synchronously made in the bone marrow. The iron released and recycled by the normal destruction of the red cells in the spleen after their life span of ~120 days is then re-used to make new red cells in the marrow … with the help of EPO.

Back to bone …

Overactive bone means that the see-saw, the balance beam has tipped off the horizontal towards increased bone reabsorption (or ‘demineralisation’). There are so many terms used for what are really quite similar basic changes in bone that it gets quite confusing (me too) …but, in essence, PTH drives increased bone turnover, bone reabsorption, bone demineralisation and is long-term ‘bad’ for bones. So … what do we do?

When the PTH is high, we try to tip the balance back to an even keel by suppressing PTH with things like active Vit D (calcitriol, paracalcitrol or whatever is the flavour of the month in Vit D in your corner of the world!) or with cinacalcet (Sensipar) or, if all fails, with a subtotal or total parathyroidectomy.

At the other end of the see-saw is adynamic bone disease. This is where PTH is flat and low, and not much (or no) bone is being made. The bone is sitting there, like a stunned mullet, doing damn all. That is just as bad for bone as being overactive and over-reabsorbed.

Bone is, in CKD and dialysis patients, a bit under-responsive to PTH so, a PTH about 2-3 times the ‘normal’ for people without kidney disease is needed to get a good balanced bone response with a balance between destruction and remodelling. That is why we dont mind when the PTH is, in yours and my units, 20-25p/ml(ish) - the upper end of normal for our lab is 8.5.

You had been, if I remember, on Vit D and cinacalcet in the past. I suspect you have overshot the mark and your PTH has gone from too high to too low - your bone from overactive to underactive.

Backing off the ‘suppressors’ is the 1st step … and you have taken that. Rome was not built in a day, Kamal … so, as long as all suppressors have been withdrawn, hang in there. It’ll take a bit of time. I wouldnt be panicking yet.

Re the low PO4 … I am still hmmmmm’ing.

Check the sample tubes!

If they are Ok … then I am struggling to find another answer.

One thing … just confirm for me that you dont have oxalosis as your primary renal disease. Oxalate can depress PO4.

Or diabetes … insulin can shift PO4 into cells … so if you are diabetic and you are giving youself insulin just as you come of dialysis … that could be a factor.

But … as you can see, I am scratching!

I’ll keep mulling over the possible reasons but that’s the best I can come up with tonight.

Hope that helps

John Agar

Thanks for your detailed response, Dr. Agar!

I actually went over to the lab and gave my blood sample two hours after dialysis. And I am sure they used a tube without EDTA.

Also, I have stopped all Vit D and cinacalcet quite some time back.

And no, I do not have oxalosis and I am not diabetic.

I have been using the F6 HPS - high flux dialysers for the last few years. I have switched to the regular F6 dialyser from the last few days. I thought the regular dialyser might remove less Phosphorus. I am not sure about that however. I just thought it might be worth trying. I will check my blood after a week or so to see if it has helped.

Thanks again Dr. Agar for helping with this!