Hypoparathyroidism, hypophosphatemia and hypercalcemia
Patient Scenario: Hypoparathyroidism, hypophosphatemia and hypercalcemia
Assessing the Clinical and Laboratory Parameters
The phosphate level is low in this patient. Chronically low phosphate levels are unusual in dialysis patients, but may be associated with osteomalacia. The presence of this constellation of parameters in a patient who has received long term aluminum-based phosphate binders is strongly suggestive of aluminum toxicity. Assess both current and previous binder use.
The PTH level is suppressed in this patient. Assess if prior parathyroidectomy, especially total removal, which may cause low PTH levels. Assess if vitamin D sterol use, as current use of vitamin D sterols in an effort to control prior hyperparathyroidism can lead to over suppression by the vitamin D sterol directly, or indirectly by the hypercalcemia. (Excessive vitamin D sterol therapy usually leads to an elevated phosphate level in addition to the hypercalcemia). Assess if calcimimetics being used, as over suppression of parathyroid glands with a calcimimetic agent is possible. Usually the use of a calcimimetics causes both hypophosphatemia and hypocalcemia.
If there is no history of a prior parathyroidectomy, this patient has hypoparathyroidism in association with high calcium. This is a normal physiologic response to hypercalcemia and suggests that the glands are not functioning autonomously. PTH levels can be expected to rise as the calcium level is brought under control.
Less than 1% of all patients are in this category.
Lowering the dialysis calcium concentration may help correct the hypercalcemia quickly, particularly if the patient is symptomatic from the hypercalcemia. This will provide a stimulus to PTH formation and secretion. Dialysate Calcium of 1 mM is available and could be used instead of the usual 1.25 or 1.5 mM Ca.