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Question #45419
The Question
A patient presents with chronic tetany. Laboratory investigations reveal severe hypocalcemia accompanied by abnormally elevated levels of Parathyroid Hormone (PTH). Assuming a genetic mutation is responsible for decoupling the PTH-calcium axis, which of the following is the most scientifically accurate explanation for this pathology?
Options
- A.
A loss-of-function mutation in the direct PTH receptors located on the surface of osteoclasts.
- B.
A loss-of-function mutation in the PTH receptors on osteoblasts, preventing subsequent osteoclast activation.
- C.
A gain-of-function mutation in the calcium-sensing receptors of the parathyroid chief cells.
- D.
Excessive secretion of Thyrocalcitonin (TCT) which competitively inhibits PTH at the renal tubules.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Regulatory_Failure
Understand how NOT, EXCEPT, and logical constraints are used to manipulate exam results.
Concepts Behind This Question
PTH|Calcitonin|Osteoclasts
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Distinguishing between glandular hyposecretion and target organ resistance, coupled with a 'Location Trap'.
Students often misinterpret the NCERT line 'PTH stimulates the process of bone resorption' by assuming PTH directly binds to osteoclasts.
In reality, PTH binds to osteoblasts, which secondarily activate osteoclasts.
This question tests both the negative feedback loop logic and micro-anatomical receptor locations.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Chemical Coordination and Integration - Class 11 |
| Concept | Feedback Mechanism Loops |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |