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NBME 23 Answers

nbme23/Block 3/Question#18

A patient with a 20-year history of type 1 diabetes ...

Impaired release of glucagon

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submitted by keycompany(127),

Type I Diabetes is characterized as the destruction of pancreatic islets (specifically beta cells) by T-cells. The most likely cause for hypoglycemia following insulin administration, therefore, is the destruction of alpha cells that surround the beta cells. This would cause decreased levels of circulating glucagon.

titanesxvi  I think rather that high insulin is going to block the release of glucagon +2  

 +2  upvote downvote
submitted by mcl(226),

According to this paper, insulin inhibits alpha cells from releasing glucagon. This is the relevant figure from the paper.

medpsychosis  There are three ways that Glucagon secretion is stimulated: +(1) a stimulatory effect of low glucose directly on the alpha cell, +(2) withdrawal of an inhibitory effect of adjacent beta cells, and +(3) a stimulatory effect of autonomic activation. The response of Glucagon to hypoglycemia is diminished in T1Diabetes. Hence in this pt, the impaired release of Glucagon allows for prolonged Hypoglycemia. Reference: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3005043/ +3  

 +1  upvote downvote
submitted by criovoly(3),

Insulin decreases the level of blood glucose and Glucagon increases levels of blood glucose. They both counter block each other. If insulin is high glucagon will be inhibited, and when glucagon is high insulin will be inhibited. FA 2018 page 76.