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A side effect of some antibiotics is to inhibit the release of thyroxine into the blood - OCR Gateway - GCSE Biology - Question 12 - 2020 - Paper 1
Question 12
A side effect of some antibiotics is to inhibit the release of thyroxine into the blood. What will these antibiotics do to levels of TSH and TRH? A Both decrease ... show full transcript
Worked Solution & Example Answer:A side effect of some antibiotics is to inhibit the release of thyroxine into the blood - OCR Gateway - GCSE Biology - Question 12 - 2020 - Paper 1
Step 1
A side effect of some antibiotics is to inhibit the release of thyroxine into the blood. What will these antibiotics do to levels of TSH and TRH?
Answer
When the release of thyroxine is inhibited, the feedback mechanism that regulates thyroid hormones comes into play. Thyroxine (T4) inhibits the release of Thyroid Stimulating Hormone (TSH) and Thyrotropin-Releasing Hormone (TRH).
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Effect on TSH: With reduced thyroxine levels, there is decreased negative feedback on the hypothalamus and anterior pituitary. This will lead to an increase in TSH secretion.
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Effect on TRH: Similarly, the reduced levels of thyroxine will likely cause an increase in TRH as the hypothalamus tries to stimulate the pituitary to release more TSH in an effort to raise thyroid hormone levels.
Therefore, both TSH and TRH levels would increase. Hence, the correct answer is B: Both increase.