Endocrinology: humoral hypercalcaemia of malignancy: practice question

A Physiology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

Try it

Physiology · Endocrinology: humoral hypercalcaemia of malignancy

Sample item

A 60-year-old smoker with squamous cell carcinoma of the lung has serum calcium 13.5 mg/dL, low serum phosphate and a suppressed PTH. Which tumour product most likely causes the hypercalcaemia?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

D. PTH-related peptide acting on the PTH receptor

Squamous cell tumours often secrete PTH-related peptide, which binds the same receptor as PTH and increases bone resorption and renal calcium reabsorption while causing phosphaturia. Raised calcium then suppresses the real parathyroid glands, so measured PTH is low.

Option by option

  • A. Calcitonin secreted by tumour cells

    Calcitonin lowers serum calcium and does not cause hypercalcaemia.

  • B. Calcitriol synthesised by tumour macrophages

    Tumour calcitriol is a mechanism of lymphoma and granulomatous disease, with low PTH but not typical of squamous cancer.

  • C. Ectopic parathyroid hormone secretion

    Ectopic PTH is rare and would show a raised PTH level, whereas PTH is suppressed here.

  • D. PTH-related peptide acting on the PTH receptor (correct)

    Correct. PTH-related peptide mimics PTH at its receptor while true PTH is suppressed.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

More Physiology questions

Questions about this Physiology question

What is the answer to this Physiology question?

The best answer is D, PTH-related peptide acting on the PTH receptor. Squamous cell tumours often secrete PTH-related peptide, which binds the same receptor as PTH and increases bone resorption and renal calcium reabsorption while causing phosphaturia.

Why is "Calcitonin secreted by tumour cells" not the answer?

Calcitonin lowers serum calcium and does not cause hypercalcaemia.

Why is "Calcitriol synthesised by tumour macrophages" not the answer?

Tumour calcitriol is a mechanism of lymphoma and granulomatous disease, with low PTH but not typical of squamous cancer.

Why is "Ectopic parathyroid hormone secretion" not the answer?

Ectopic PTH is rare and would show a raised PTH level, whereas PTH is suppressed here.

What concept does this question test?

It tests Endocrinology: humoral hypercalcaemia of malignancy in Physiology. Raised calcium then suppresses the real parathyroid glands, so measured PTH is low.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Endocrinology: humoral hypercalcaemia of malignancy?

For each system, sketch the key graph (pressure–volume loop, oxygen dissociation curve, nephron handling) and explain it aloud. Then use the flashcards and the other Physiology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.