Desired PTH, hyperphosphatemia and low or normal calcium

Patient Scenario: Desired PTH, hyperphosphatemia and low or normal calcium



Assessing the Clinical and Laboratory Parameters

Phosphate control is suboptimal in this patient. 

The PTH level is at the target range in this patient.  This may be as a result of current use of vitamin D sterols in an effort to control hyperparathyroidism.  However, it may be that the vitamin D sterol is adversely influencing phosphate balance by increasing absorption.

Approximately 4% of all patients are in this category.

Therapeutic Options:

{tab=Dialysis Prescription}

Dialysis Prescription

A reduction in dialysate calcium may permit an increase in the amount of calcium containing binder that could be used without inducing hypercalcemia.  Significant prolongation of dialysis time, specifically nocturnal, would enhance phosphate clearance.

{tab=Phosphate and Calcium Management}

Phosphate and Calcium Management

Ongoing counseling about phosphate in the diet, persistence and the timing of binders with respect to meals is required.  The dose and type of binders could be increased.  An increase of just calcium containing binders would be expected to lower the phosphate and the PTH, but may result in hypercalcemia (particularly if a vitamin D sterol is also being used).  A magnesium based binder could be added.  If the patient has had problems with hypercalcemia in the past, it may be reasonable to add in a non calcium containing binder instead of increasing the dose of the calcium based binder.  A short (less than 3 month) course aluminum based binders should be reserved for severe hyperphosphatemia, or hyperphosphatemia refractory to other therapeutic maneuvers.

A reduction in vitamin D sterol dose may be helpful if coupled with an increase in the dose of calcium-containing phosphate binder.  Simply raising the calcium-containing phosphate binder may result in some amelioration of the hyperphosphatemia, but is also likely to reduce the PTH level and may precipitate hypercalcemia.



{tab=PTH Management}

PTH Management

Since the PTH is at the target, no change in the calcimimetic dose (if used) is indicated. There is no indication to initiate calcimimetic use in this patient since efforts to control the phosphate here may move the PTH out of target, most likely in the downward direction.


{tab=Other Options of Controversies in Management}

Other Options of Controversies in Management

The area of which type and dose of binder remains controversial due to the lack of data and information on both on safety and efficacy beyond phosphate lowering. Concerns over calcium load are mostly based on observational studies and basic science findings. Calcium as a phosphate binder has not been rigorously evaluated, and  recent meta analyses comparing Calcium to non calcium based binders have been done which highlight the lack of data to inform clinical care.

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Suggested References

1. Jamal SA, Fitchett D, Lok CE, Mendelssohn DC, Tsuyuki RT. The effects of calcium-based versus non-calcium-based phosphate binders on mortality among patients with chronic kidney disease: a meta-analysis. Nephrol Dial Transplant 2009;24:3168-74

2. St Peter WL, Fan Q, Weinhandl E, Liu J.,  Economic evaluation of sevelamer versus calcium-based phosphate binders in hemodialysis patients: a secondary analysis using centers for Medicare & Medicaid services data. Clin J Am Soc Nephrol. 2009 Dec;4(12):1954-61. Epub 2009 Oct 15.

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