Hypercalcaemia of malignancy is best described as which of the following?

Hypercalcaemia of malignancy is best described as which of the following?

• A. Elevated serum calcium due to tumour activity or osteolytic metastases
• B. Low serum calcium due to malnutrition
• C. Normal calcium with dehydration
• D. Elevated phosphate only

Answer: (A)

Hypercalcemia of malignancy occurs when cancer drives calcium into the bloodstream, either by tumor activity that promotes bone breakdown or by osteolytic metastases that release calcium from bone. The key idea is that malignancy elevates serum calcium through these mechanisms, leading to high calcium levels in the blood. This fits because tumors can secrete humoral factors like PTH-related peptide that mimic PTH, increasing bone resorption and renal calcium reabsorption, or because cancer metastases in bone cause localized bone destruction and calcium release. The other options describe situations that don’t capture this malignant mechanism: malnutrition tends to lower calcium, dehydration alone doesn’t define the malignant process, and having elevated phosphate only isn’t the characteristic pattern of hypercalcemia seen with cancer (phosphate can be normal or low depending on the mechanism).

Hypercalcemia of malignancy occurs when cancer drives calcium into the bloodstream, either by tumor activity that promotes bone breakdown or by osteolytic metastases that release calcium from bone. The key idea is that malignancy elevates serum calcium through these mechanisms, leading to high calcium levels in the blood.

This fits because tumors can secrete humoral factors like PTH-related peptide that mimic PTH, increasing bone resorption and renal calcium reabsorption, or because cancer metastases in bone cause localized bone destruction and calcium release. The other options describe situations that don’t capture this malignant mechanism: malnutrition tends to lower calcium, dehydration alone doesn’t define the malignant process, and having elevated phosphate only isn’t the characteristic pattern of hypercalcemia seen with cancer (phosphate can be normal or low depending on the mechanism).