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* Thyroid Pathology question help
 #846071  
  smm123 - 12/05/17 04:45
 
  Can someone please help explain how this is possible. I've encountered a question that states,"Pt has 1 year of fatigue, constipation, ans muscle cramps during exercise. Thyroid panel reveals low TSH, low total T4, and low total T3. What is the most likely diagnosis"?

A. Hyperthyroidism due to Graves Disease
B. Hypothyroidism due to Hashimoto disease
C. Hypothyroidism due to Iodine deficiency
D. Hypothyroidism due to pituitary insufficiency
E. Hypothyroidism due to treatment with excess PTU

I chose answer D as a guess, but I'm confused how T4 is low but T3 is normal. Any pathological explanation is appreciated.
 
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* Re:Thyroid Pathology question help
#3354281
  bensha - 12/05/17 10:34
 
  smm123,

you mentioned in the question stem low total T3. But again at the end u say its normal?

If its also low like mentioned in the q stem, then its answer D.
 
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* Re:Thyroid Pathology question help
#3354360
  halux - 12/05/17 17:37
 
  check the diagram of FA 17 p.321

SECONDARY HYPOTHYROIDISM is caused by ANTERIOR PITUITARY INSUFFICIENCY
--> NO TSH SECRETED --> NO THYROID FOLLICULAR CELLS STIMULATED --> NO T4 AND T3 SECRETED

 
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* Re:Thyroid Pathology question help
#3354369
  smm123 - 12/05/17 18:10
 
  I apologize the original question stem should state NORMAL T3.  
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* Re:Thyroid Pathology question help
#3354371
  smm123 - 12/05/17 18:13
 
  Halux:

Would the low TSH not be do to the normal T3 and negative feedback shutting down the Pituitary? That is why I am confused. How can T4 be low and T3 be normal?
 
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* Re:Thyroid Pathology question help
#3354488
  halux - 12/06/17 18:51
 
  @smm123

Both T3 and T4 have negative feedback over TRH and TSH stimul, not only T3.

Not sure about the normal T3 level on that Q's stem.

The only way T3 level can be different is due to exogenous T3 intake,
but in that case everything will be decreased except T3 that is increased.

Check again the Question details like a possible Rx or a clue that support that value otherwise if it is from an old nbme just forget about that...

**Maybe if someone know something and can clarify this would be good.
 
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