Help! Quick thyroid hormone question from Kaplan online workshop

[jiejsun]

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A person with hyperthyroidism tested for T3, T4, and TSH levels. You expect levels to be:

Answer: T4, T3 high, TSH low

My question: shouldn't TSH level be high as well? Since hyperthyroidism is represents abnormal functioning. I was thinking that in normal individuals, we'd have low TSH in response to high T4 T3 levels(neg feedback), but not in ppl with hyperthyroidism. Where am I thinking wrong here?

 

[dsoz]

A person with hyperthyroidism tested for T3, T4, and TSH levels. You expect levels to be:

Answer: T4, T3 high, TSH low

My question: shouldn't TSH level be high as well? Since hyperthyroidism is represents abnormal functioning. I was thinking that in normal individuals, we'd have low TSH in response to high T4 T3 levels(neg feedback), but not in ppl with hyperthyroidism. Where am I thinking wrong here?

I am going from memory here, so I may have some details wrong.

If the hyperthyroidism is from a thyroid tumor, then the excess T3 T4 would negative feedback to TRH to decrease TSH.

If the hyperthyroidism is from a hypothalamus tumor or an anterior pituitary tumor than the TRH and/or TSH levels would be high as well. But I think that increased TRH also messes with another hormone (I think prolactin...?) so if it has a normal level then TRH would not be high.

dsoz

 

[ttpharm]

A person with hyperthyroidism tested for T3, T4, and TSH levels. You expect levels to be:

Answer: T4, T3 high, TSH low

My question: shouldn't TSH level be high as well? Since hyperthyroidism is represents abnormal functioning. I was thinking that in normal individuals, we'd have low TSH in response to high T4 T3 levels(neg feedback), but not in ppl with hyperthyroidism. Where am I thinking wrong here?

Youre getting too technical. Yes there is some negative feedback, but the main answer is high levels of thyroxin (T4 and T3). If you can only choose 1 answer, then T4. Since its the most abundant and converts to T3 at tissues.