Question

Assertion (A): Lack of insulin or thyroid hormone increases blood cholesterol, whereas excess thyroid hormone decreases it. Reason (R): These effects are probably caused by changes in the degree of activation of specific enzymes responsible for the metabolism of lipid substances.

• A. Both (A) and (R) are correct and (R) is the correct explanation of (A).
• B. Both (A) and (R) are correct but (R) is NOT the correct explanation of (A).
• C. (A) is correct but (R) is not correct.
• D. (A) is not correct but (R) is correct.

Hint:

Thyroid hormone is the “metabolic furnace.” High heat (excess hormone) burns off the cholesterol.

Answer 1

The Correct Option is A

Step 1: Concept
Hormones regulate the rate of metabolic pathways, including lipid synthesis and breakdown.

Step 2: Meaning
Thyroid hormones generally speed up metabolism, including clearance of cholesterol.

Step 3: Analysis
Assertion (A) states a known medical fact. Reason (R) explains the how: hormones act as signalling molecules that turn enzymes on or off, thus decreasing blood cholesterol levels when thyroid hormone is high.

Step 4: Conclusion
(R) explains the biochemical mechanism behind the observation in (A).

Final Answer: (A)