Parathyroid: secondary hyperparathyroidism: practice question

A General Surgery 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

General Surgery · Parathyroid: secondary hyperparathyroidism

Sample item

A haemodialysis patient has persistently raised PTH, high phosphate and low-normal calcium despite phosphate binders and vitamin D analogues. Cinacalcet is added. What is its mechanism?

AInhibition of osteoclast activityBActivation of the vitamin D receptorCAllosteric activation of the calcium-sensing receptor on the parathyroid cellDBinding of dietary phosphate in the gut

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

The answer and the reasoning

C. Allosteric activation of the calcium-sensing receptor on the parathyroid cell

Cinacalcet is a calcimimetic that sensitises the calcium-sensing receptor to extracellular calcium, so PTH secretion falls along with calcium and phosphate. It is used in secondary hyperparathyroidism of chronic kidney disease and in inoperable primary disease. Hypocalcaemia is its main adverse effect.

Option by option

A. Inhibition of osteoclast activity
Osteoclast inhibition is the effect of bisphosphonates and denosumab.
B. Activation of the vitamin D receptor
Vitamin D receptor activation is the action of calcitriol and paricalcitol.
C. Allosteric activation of the calcium-sensing receptor on the parathyroid cell (correct)
Correct. Calcimimetics lower PTH by increasing receptor sensitivity to calcium.
D. Binding of dietary phosphate in the gut
Phosphate binding is the action of sevelamer and calcium carbonate.

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.

Questions about this General Surgery question

What is the answer to this General Surgery question?

The best answer is C, Allosteric activation of the calcium-sensing receptor on the parathyroid cell. Cinacalcet is a calcimimetic that sensitises the calcium-sensing receptor to extracellular calcium, so PTH secretion falls along with calcium and phosphate.

Why is "Inhibition of osteoclast activity" not the answer?

Osteoclast inhibition is the effect of bisphosphonates and denosumab.

Why is "Activation of the vitamin D receptor" not the answer?

Vitamin D receptor activation is the action of calcitriol and paricalcitol.

Why is "Binding of dietary phosphate in the gut" not the answer?

Phosphate binding is the action of sevelamer and calcium carbonate.

What concept does this question test?

It tests Parathyroid: secondary hyperparathyroidism in General Surgery. It is used in secondary hyperparathyroidism of chronic kidney disease and in inoperable primary disease. Hypocalcaemia is its main adverse effect.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. 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 Parathyroid: secondary hyperparathyroidism?

Learn classic signs and eponyms alongside what they diagnose. Then use the flashcards and the other General Surgery 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.