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Question #45422
The Question
A patient presents with a hyperactive thyroid tumor. Blood analysis reveals highly elevated Thyroxine (T4) levels and nearly undetectable Thyroid Stimulating Hormone (TSH). When these tumor cells are cultured in vitro, they exhibit continuous proliferation and T4 synthesis even in a completely TSH-free medium. Which of the following best explains this physiological anomaly?
Options
- A.
A mutation in a proto-oncogene has resulted in constitutively active downstream signaling, rendering the cells independent of TSH.
- B.
The anterior pituitary has lost its sensitivity to the negative feedback of T4, causing unregulated thyroid stimulation.
- C.
Loss of contact inhibition in the thyroid cells has directly stimulated the hypothalamus to secrete continuous TRH.
- D.
The thyroid cells have developed a loss-of-function mutation in their TSH receptors, triggering compensatory hypersecretion.
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
Oncogenes|Proto-oncogenes|Pituitary_Axis
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often assume that hypersecretion of a target gland hormone must be due to a failure of negative feedback at the pituitary level.
The trap is failing to integrate the concept of oncogenes (from Human Health and Disease) with endocrine regulation (Chemical Coordination).
Recognizing that undetectable TSH proves the pituitary feedback is working perfectly forces the student to deduce that the defect is autonomous to the target gland via oncogenic transformation.
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 |