crista
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A child is 2 standard deviations below the expected mean height for his age. He also has delayed bone
maturation and a goiter. Analysis of genetic material reveals a point mutation in the thyroid hormone receptor.
Which of the following laboratory results would be expected in this patient?
A. Decreased radioactive iodine uptake test (RAIU)
B. Decreased resin T3 uptake test
C. Decreased plasma TSH concentration
D. Increased basal metabolic rate (BMR)
E. Increased plasma T4 concentration
I don't understand the answer that is E. May be somebody could help me.
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| rida
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My understanding, if mutation is in the thyroid hormone receptor, the hormone cannot bind it, therefore its concentration in the plasma would increase.
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| mdwannabe
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For the same reason as why in LDL receptor mutaion you get hyper LDL (type IIa)
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| Quinn
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Right! In addition my understand is that T4 is required for growth...it is permissive for normal growth hormone function. So, I think that is why the child has delayed bone maturation and is short.
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| Idiopathic
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The answer is E because the production/stimulation of T4 is not affected, just its utilization. this patient will be hyperthyroid due to overproduction, but will manifest clinically as hypothyroid. Also, it is safe to assume that if the peripheral receptor is affected that the feedback receptor in the hypothalamus/pituitary could also be affected.
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| Malaysian
Forum Guru
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Posts: 778
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Do they ask these sort of questions in the USMLE?
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