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nbme24/Block 3/Question#44

A 62-year-old man comes to the physician for a ...

Serum gastrin

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 +10  upvote downvote
submitted by neonem(366),

I think the idea here is that if you take someone off a PPI, if there's no neoplasm or any problem with gastrin production then you should see it go down from baseline due to more negative feedback of gastric acidity. If not, you probably have a neoplasm that's just making tons of gastrin, such as in the case of Zollinger-Ellison syndrome.

gonyyong  I thought it was that if you are taking a PPI, you will see elevated gastrin regardless of it you have a gastrinoma. Thus to confirm diagnosis, you make them stop taking it, then re-measure gastrin → if it's still high, you have confirmed. If it's normal, it's something else +15  

 +2  upvote downvote
submitted by welpdedelp(137),

I thought this was just referencing zollinger ellison, which would have elevated gastrin

 +2  upvote downvote
submitted by diabetes(10),

When ZES is suspected, the initial test recommended is a fasting serum gastrin (FSG) determination in the absence of antisecretory therapy (Sensitivity- 98–100% in ZES patients various series. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5757869/

The use of any agent that inhibits gastric secretion of acid (H2-receptor antagonists or PPIs) will result in a rise in serum gastrin as the feedback inhibition of gastrin release is diminished.

If you want to rule out Zollinger-Ellison syndrome you need to stop the PPIs first, then measure Gastrin to make that your intial measure of elevated Gastrin was not due to your drug rather than the patients disease.

 +1  upvote downvote
submitted by dentist(17),

To me: this seemed more straightforward. You'd want to follow up and check Gastrin levels on a patient who previously had 4x normal.

thotcandy  He could have 4x the normal because of current PPI use. the point was that you'd get him off, wait for it to normalize, then check again to see if it's due to neoplasm or PPIs +