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Kaplan Qbank USMLE



Author7 Posts
  #1

UW says T3 controls negative feedack of TSH and KLN says T4 does. so which one is it?

thanks for the answer, and i hope everyone's reading is going satisfactory?wink


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  #2

T4 is considered to be main Regulator of TSH this is wht i know but further confirm it for u and me grinwink

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  #3

http://www.prep4usmle.com/forum/comments.php?id=4...

  #4

Ganong says that circulating T3 is the principal feedback regulator of TSH secretion (p.328).




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  #5

However, Ganong also mentions "TSH secretion is inhibited in a negative feedback fashion by circulating free T4 & T3. The effect of T4 is enhanced by production of T3 in the cytoplasm of the pituitary cells". <<--and i think it's this last concept that KLN also mentions

Edited by silver on 06/22/07 - 12:06 PM

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  #6

very very HY concept ! Kaplan does a great job ...
T3 molecules create the negat. feedback, circulating T4 is converted into intracellular T3 within the tyrotroph cells.
Circulating T3 creates a very little - feedback bc under N cond. is very little circ. T3 !
Abnormal sit---->if inducing nonphysiologically incr. circulating T3( injection of T3)--->incr - feedback-->decr THS


  #7

thanks for the link, me007. very informative. in fact, that's exactly where i came across it, and the qn is also the same, and i did get it wrong. so the confusion still prevails! and nobody has got the definitive answer.

this qn better not show up on my exam, coz i'd know both the right answers, and wouldn't be able to decide which to pick!


___________________
Prepare as if you're the worst, Perform as if you're the best! As you dream, so you manifest. So, DREAM BIG!! When you face hardship, remember, God never gives you more than you can handle. Keep your face to the sunshine and you cannot see the shadows.







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