Hypercalcemia associated with malignancy is most often mediated by \ \ \ \ \ \ \ ? - Chitranjjan National Cancer Institute Kolkata - 2021

Chitranjjan National Cancer Institute Kolkata - 2021

Medical & Surgical Nursing

Easy

Appeared in: Chitranjjan National Cancer Institute Kolkata - 2021

Explanation

Hypercalcemia of malignancy is most commonly caused by the secretion of Parathyroid Hormone-related protein (PTH-rp) by tumor cells.
This mechanism, known as Humoral Hypercalcemia of Malignancy (HHM), accounts for approximately 80% of cases.
PTH-rp mimics the action of PTH on bone and kidneys, increasing bone resorption and calcium reabsorption, which raises blood calcium levels.
A key diagnostic feature is that while PTH-rp is high, the body's own PTH level is suppressed due to negative feedback from the high calcium.

Option A: Ectopic secretion of actual PTH by a tumor is extremely rare. In most cases of malignancy-related hypercalcemia, the parathyroid glands are suppressed by the high calcium, leading to low PTH levels.
Option C: While Interleukin-6 (IL-6) and other cytokines cause hypercalcemia, they do so through local bone destruction by metastases. This is a less common overall cause than the systemic effects of PTH-rp.
Option D: Calcitonin has the opposite effect; it is a hormone that works to lower blood calcium levels by inhibiting osteoclast activity and increasing renal calcium excretion.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Pathophysiology of hypercalcemia of malignancy as background academic context rather than a clinical decision trigger.
Nurses caring for patients with cancer, especially lung, breast, kidney, and multiple myeloma, must be vigilant for signs of hypercalcemia: confusion, lethargy, nausea, constipation, and polyuria ('bones, stones, groans, and psychic moans').
Accurate diagnosis is critical for management. A lab profile showing high calcium, high PTH-rp, and low PTH is characteristic of HHM.
Management of malignancy-related hypercalcemia involves hydration, bisphosphonates, and treating the underlying cancer.

How to Approach the Question

First, identify the key terms in the question: 'Hypercalcemia,' 'malignancy,' and 'most often.' The question is asking for the most frequent cause of high calcium in cancer patients.
Recall the major hormones and factors involved in calcium regulation: PTH (raises calcium), Calcitonin (lowers calcium), and Vitamin D.
Consider how cancer disrupts this normal regulation. Tumors can produce substances that mimic hormones (paraneoplastic syndrome) or directly destroy bone.
Evaluate each option in the context of being the 'most common' cause:
PTH: Is ectopic secretion by tumors common? No, it's known to be very rare.
PTH-rp: Is this a known paraneoplastic product? Yes, it's the basis for Humoral Hypercalcemia of Malignancy (HHM), a well-documented and common cause.

Concept Tested & Keywords

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E6 Pathology- ROBBINS & COTRAN PATHOLOGIC BASIS OF DISEASE 10TH Ed p. 1094-1096