Define Hypercalcemia.
Hypercalcemia is a total serum calcium concentration of > 10.5 mg/dL (> 2.62 mmol/L) or ionized (free) calcium concentration of > 5.25 mg/dL (> 1.31 mmol/L).
Define True hypercalcemia.
↑ ionized calcium or ↑ corrected calcium (regardless of total calcium level); can be symptomatic.
Define factitious hypercalcemia.
↑ total calcium with normal ionized (non-protein bound, physiologically active) calcium or normal corrected calcium level; asymptomatic.
The increase in total serum calcium levels is caused by increased protein levels, for example:
Hyperalbuminemia in dehydrated patients
Paraproteinemia in patients with multiple myeloma.
PTH-mediated hypercalcemia (table).
Non-PTH-mediated hypercalcemia (table).
What should be remembered in terms of primary hyperparathyroidism vs. hypercalcemia of malignancy?
In primary hyperparathyroidism, serum calcium is typically lower and rises more slowly than in hypercalcemia of malignancy. Patients are, therefore, less symptomatic.
Menmonic causes hypercalcemia.
For causes of hypercalcemia, remember “Thinking Chimpanzees!”Thinking: Thiazides, thyroidCalcium supplementationHyperparathyroidismImmobilization, inherited (FHH)Milk-alkali synd., meds (thiazides, lithium)Paraneoplastic PTHrPAdrenal insufficiencyNeoplasm (multiple myeloma, breast, lung)Zollinger-Ellison syndromeExcessive vitamin DExcessive vitamin ASarcoidosis & granulomatous diseases
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