Question at position 8 If you administer a drug that is designed to block the release of Thyroid Releasing Hormone, you would expect to see:Increased metabolic rateDecreased concentration of thyroid hormoneDecreased metabolic rateA and BB and C单项选择题
A
Increased metabolic rate
B
Decreased concentration of thyroid hormone
C
Decreased metabolic rate
D
A and B
E
B and C

Question

Question at position 8 If you administer a drug that is designed to block the release of Thyroid Releasing Hormone, you would expect to see:Increased metabolic rateDecreased concentration of thyroid hormoneDecreased metabolic rateA and BB and C单项选择题

A

Increased metabolic rate

B

Decreased concentration of thyroid hormone

C

Decreased metabolic rate

D

A and B

E

B and C

BlackTom AI · Accepted Answer

Thyrotropin-releasing hormone (TRH) from the hypothalamus normally stimulates the anterior pituitary to secrete thyroid-stimulating hormone (TSH), and TSH in turn stimulates the thyroid gland to produce thyroxine (T4) and triiodothyronine (T3), which raise basal metabolic rate. Blocking TRH therefore disrupts this hypothalamic–pituitary–thyroid axis and lowers downstream activity.

1) Relevant knowledge points and concepts
- TRH → stimulates anterior pituitary to release TSH.
- TSH → stimulates thyroid to produce T3 and T4.
- T3/T4 → increase metabolic rate (increase O2 consumption, heat production, and basal metabolic processes).
- Negative feedback: T3/T4 normally suppress TRH and TSH, but if TRH is pharmacologically blocked the compensatory increase in TRH cannot occur.

2) Step-by-step reasoning
Step 1: Drug blocks TRH release from the hypothalamus.  
Step 2: With less TRH, the anterior pituitary secretes less TSH.  
Step 3: Lower TSH leads to reduced stimulation of the thyroid gland, so T3 and T4 secretion falls.  
Step 4: Reduced T3/T4 levels decrease basal metabolic rate (slower metabolism).  
Step 5: Although low thyroid hormones normally would lead to increased TRH/TSH by feedback, the drug prevents TRH increase, so thyroid hormone remains low.

3) Intermediate steps (logic chain)
TRH↓ → TSH↓ → T3/T4↓ → metabolic rate↓.

4) Why the correct answer is correct
Options B and C together state “Decreased concentration of thyroid hormone” and “Decreased metabolic rate,” which follow directly from the chain above. Blocking TRH reduces TSH and therefore reduces thyroid hormone production; reduced thyroid hormone causes a lowered metabolic rate.

5) Why other options are incorrect
- “Increased metabolic rate” (A) is opposite to the physiological consequence of lowering thyroid hormones.  
- “A and B” (D) pairs an increase in metabolic rate with decreased thyroid hormone, which is contradictory and thus incorrect.  
- Any option claiming increased metabolism cannot be correct when the hormonal drive for thyroid hormone is inhibited.

6) Conclusion
Therefore the correct choice is B and C (Decreased concentration of thyroid hormone and Decreased metabolic rate), matching the provided answer.