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Question #45749
The Question
A 60-year-old patient with metastatic lung carcinoma presents with severe dilutional hyponatremia (abnormally low blood sodium concentration) and highly concentrated urine, despite having a low blood plasma osmolality. This paraneoplastic syndrome is caused by the ectopic secretion of a specific hormone by the tumor cells. Which of the following statements correctly identifies the hormone and explains the physiological breakdown occurring in this patient's renal system?
Options
- A.
Ectopic Vasopressin forces obligate water reabsorption in the Proximal Convoluted Tubule, diluting the blood plasma and washing out the medullary gradient.
- B.
Ectopic Aldosterone stimulates excessive Na+ and water reabsorption in the Distal Convoluted Tubule, leading to dilutional hyponatremia.
- C.
Ectopic Vasopressin forces excessive facultative water reabsorption in the distal convoluted tubule and collecting duct, overriding the normal hypothalamic osmoreceptor feedback.
- D.
Ectopic Vasopressin suppresses the counter-current multiplier, actively inhibiting NaCl transport from the ascending limb of the Loop of Henle.
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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
Neoplasm|Metastasis|ADH_Secretion
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Distinguishing between 'obligate' (PCT) and 'facultative' (DCT/CD) water reabsorption, and understanding the negative feedback loop of osmoreceptors.
The trap relies on students confusing the exact location of ADH action (Location Trap) or misunderstanding how an ectopic tumor secretion decouples a hormone from its normal homeostatic feedback mechanism (Application of NCERT Chemical Coordination and Excretory Products).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Excretory Products and Their Elimination - Class 11 |
| Concept | Tubular Secretion Specificity |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |