Hypoparathyroidism, hypophosphatemia and low or normal calcium

Patient Scenario: Hypoparathyroidism, hypophosphatemia and low or normal calcium

 

Assessing the Clinical and Laboratory Parameters

Long term hypophosphatemia may be associated with osteomalacia. Assess dietary intake, nutritional status and binder use.

Assess if prior parathyroidectomy, which can result in low PTH, especially if a total removal was done.  If so, this constellation of biochemical findings suggests an imbalance between the vitamin D sterol replacement and the calcium replacement.

If no prior parathyroidectomy, this patient has hypoparathyroidism in association with normal or low calcium. There should be a natural stimulation to enhanced PTH production here if the calcium is low.

Assess use of medications, especially calcimimetics. Over suppression of parathyroid glands with a calcimimetic agent is possible in this patient, and the presence of hypophosphatemia and a normal or low calcium increases the likeliehood that any calcimimetic being used is in excessive dose. 

Less than 1% of all patients are in this category.

Therapeutic Options:

{tab=Dialysis Prescription}

Dialysis Prescription

Depending on the phosphrous level, additional PO4 may need to be added to the dialysate. Dialysate calcium bath should be individualized to correct serum calcium into the normal range. Increasing calcium bath may further suppress the PTH level.

{tab=Phosphate and Calcium Management}

Phosphate and Calcium Management

Liberalization of the diet may help raise the phosphate level.  If there is significant cachexia, intradialytic TPN may be considered after modification of the diet and supplements.   The dose of calcium containing phosphate binder in this patient needs to be reassessed given the presence of both normal or low calcium and hypophosphatemia.  A decrease in calcium dose given with meals, and a switch to calcium supplementation away from times of food ingestion may improve both parameters.  If the calcium is normal, a simple reduction in binder dose may be all that is required.  If the patient is being managed primarily with non-calcium containing binders, the dose should be reduced. Aluminum containing binders should be discontinued.

A Vitamin D sterol will increase both calcium and phosphate absorption and may return both these parameters to normal, but may further suppress the PTH level.

{tab=PTH Management}

PTH Management

Although the use of vitamin D seems unlikely given that both the calcium and the phosphate are low, it should be discontinued while liberating the dietary phosphate and providing calcium supplementation.

If a Calcimimetic is being used it should be discontinued until the PTH starts to exceed the target range.

 

{tab=Other Options of Controversies in Management}

Other Options of Controversies in Management

Although therapeutic use of teriparatide is being considered for patients who fall into this group, such an approach is currently experimental.

 

 

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Suggested References

1. Puig-Domingo M, D?´az G, Nicolau J, Ferna´ndez C, Rueda S, Halperin I. Successful treatment of vitamin D unresponsive hypoparathyroidism with multi pulse subcutaneous infusion of teriparatide. Eur J Endocrinol. 2008; 159:653–657.

2.  Mahajan A, Narayanan M, Jaffers G, Concepcion L. Hypoparathyroidism associated with severe mineral bone disease postrenal transplantation, treated successfully with recombinant PTH Hemodial Int. 2009 Oct;13(4):547-50. Epub 2009 May 28

3. A Clinical Trial “The Effects of Ibandronate or Teriparatide Therapy on Bone Histology and Biochemical Indices in Patients on Hemodialysis With Low Bone Mineral Density” at Clinical Trials.Gov  http://www.clinicaltrials.gov/ct2/show/NCT00446589?term=Teriparatide&cond=hemodialysis&rank=1