What are the different types of non-parathyroid hormone (PTH)-mediated hypercalcemia?

Updated: Apr 11, 2018
  • Author: Thomas E Green, DO, MPH, MMM, CPE, FACEP, FACOEP; Chief Editor: Romesh Khardori, MD, PhD, FACP  more...
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Answer

Non–PTH-mediated hypercalcemia includes the following:

  • Hypercalcemia associated with malignancy: Unlike PTH-mediated hypercalcemia, the elevation of calcium that results from malignancy generally worsens until therapy is provided. Hypercalcemia caused by malignancy is the result of increased osteoclastic activity within the bone. This results from one or both of the mechanisms that follow:

    • Extensive localized bone destruction may result from osteolytic metastasis of solid tumors. Evidence indicates that many malignant cells may release local osteoclastic activating factors.

    • Increased calcium levels resulting from malignancy caused by a PTH-related protein (PTH-rp) is a second mechanism. This protein is a humeral factor that acts on the skeleton to increase bone reabsorption; it acts on the kidney to decrease excretion of calcium. The gene that produces this protein is present in many malignant tissues.

  • Granulomatous disorders: High levels of calcitriol may be found in patients with sarcoidosis and other granulomatous diseases. In these disorders, the increased level of calcitriol results from production within the macrophages, which constitute a large portion of some granulomas.

  • Iatrogenic: In some cases, elevation of calcium is a known adverse effect of appropriate dosage. In other cases, large ingestions must be taken to induce the increase in calcium levels. Obtain a complete review of current medications for patients presenting with hypercalcemia. Record any vitamin use.


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