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From Bone to Health
Dr Pearl Pai
Consultant Nephrologist, Royal Liverpool University Hospital
‘The bone is a dynamic tissue and constantly the bone cells are making new bones and repairing old bone tissue. To be able to do this you need normal bone minorization. The parathyroid gland works on the bone, the kidney and the gut to try to maintain the normal calcium levels of the bone. But there is a condition called secondary hyperparathyroidism, which often develops in patients with kidney failure. So what does uncontrolled parathyroidism do to you? What has been the conventional therapy and what are its shortfalls? And how does the new Calcimetic agent, available since April 2005 work?
When the kidney function declines, the parathyroid gland hormones start to rise and in time this can lead to little nodules forming on this big juicy gland at the bottom of your neck. These are usually non responsive to surgery and so removal of the parathyroid gland becomes necessary. An uncontrolled parathyroidism can make you itch and suffer with bone pain and sometimes mood swings. It can also aggravate your blood pressure control, make you less responsive to EPO and, in severe cases, can cause fibrosis to your cardiac muscle.
The cardio risk factor is higher in kidney failure patients than in diabetic patients or those with high blood pressure. Our patients also suffer with renal anaemia, an additional stress factor due to dialysis, raised PTH levels and now we also know that an increase in phosphate and calcium phosphate products present an additional risk.
Ideally the patient phosphate level will be lower than at present but there is no real evidence to support what is the best level and we can see that our results are similar to those achieved in Germany, France and the USA. The reason for this is the limited availability of phosphate restriction; phosphate binders are too big, too many to take, too unpalatable and you don’t like them!
So this new Calcimetic agent is different.
Mimpara (Cinacalcet) is a new oral Calcimetic agent available to use in the U.K. for treatment of secondary hyperparathyroidism in dialysis patients. Clinical trials involving over a thousand dialysis patients have demonstrated efficacy in most patients with moderately severe hyperparathyroidism. By acting directly on the parathyroid gland, Mimpara does not induce hypercalcaemia, a commonly encountered problem with conventional therapy using calcium-containing phosphate binders and vitamin D supplement.
For all our special cases in Mersey and Cheshire we have come up with a locally developed guideline so that all patients who require the therapy will receive it. These are the patients who have failed to respond to conventional therapy, have hypocalcaemia, those who have a relapse post parathyroidectomy and those who are not suitable for this operation. I urge the different KPA representatives here today to develop your own guidelines so that those patients who need this therapy may receive it.
Ultimately for those of you who are suitable for kidney transplantation, we need to continue to promote organ donation because that remains still the very best treatment for kidney patients.
Question 1: I have been on dialysis for 20 years and in June I had my third parathyroidectomy, which my consultant said would cure me for the time being. He also said I was an ideal candidate for this new drug so when will it be available?
Dr Pai: The drug has been licensed since April 2005 in this country.
Question 2: You mentioned the effect of cardiac calcification on long term dialysis, but to what extent is this danger reduced after transplantation?
Dr Pai: Kidney transplantation is the best treatment but unfortunately only about 25% of our patients are ever on the waiting list at any time because many are not fit enough for other reasons associated with their condition.
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