new_n_lost
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A patient has an insulin-secreting tumor that is localized to the tail of the pancreas. Which of the following would most likely be an associated finding during fasting?
A. Glycosylated hemoglobin level is increased
B. Plasma concentration of C peptide is decreased
C. Plasma concentration of glucagon is decreased
D. Plasma concentration of glucose is increased
E. Plasma concentration of proinsulin is increased
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| mytime
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C>>>>>>>>>> coz glucagon is inhibited in presence of insulin. And anyway rest don't go.
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| jole
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C
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| new_n_lost
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 Think Again Ladies
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| mytime
Kick my butt!
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OK let's look at it this way can't be A...coz that increases in DM.
B. C peptide should be increased not decreased.
D.Plasma conc. of glucose has to be decreased with all that insulin in blood.
E. Proinsulin is increased but that's not what u see, riht? so didn't pick that one...but igues that's what they want.
SO EEEEEEEEEEEEEEEEEEEEEEE.
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| mytime
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| new_n_lost
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Now She gets it GooD Job Mytime
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| new_n_lost
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The correct answer is E.
Hypersecretion of insulin by a pancreatic b cell tumor is a major cause of fasting hypoglycemia (plasma glucose is not increased, choice D). Symptoms are related to neuroglycopenia and could include recurrent central nervous system dysfunction during fasting or exercise. While proinsulin only makes up approximately 20% of plasma immunoreactive insulin in normal individuals, in patients with an insulinoma it contributes 30-90% of the immunoreactive insulin. Hence, plasma levels of proinsulin are increased.
The increased secretion of insulin by the tumor will also lead to an increase in C peptide secretion (not decreased, choice B) since b cells secrete insulin and C peptide on a one-to-one molar ratio.
Given the prolonged hypoglycemia, the amount of glycosylated hemoglobin may also be decreased, although this is not a universal finding. Certainly, an increase in glycosylated hemoglobin would not be expected (choice A).
Glucagon secretion is increased by hypoglycemia and its plasma level in a patient with an insulinoma would be expected to be increased compared to normal (not decreased, choice C)
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| chemamr
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agree with E
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