ACTH Producing Pituitary tumor

[pathtopenn]

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Under the Endocrine section of 1st Aid of Cushing's Syndrome in the sidebar.

It says that for a Dexamethasone test:

ACTH-producing pituitary tumor inc cortisol after low dose and dec cortisol after high dose.

I am kind of confused on this statement.

My reasoning is this:
ACTH is elevated in this case coming from ant pit = > cortisol production is high after low dose......this part I understand b/c the negative feedback is important.

What's after this is what confused me....
dec cortisol after high dose

Could someone please explain this part to me or refer me to any text that may explain this part better. Thanks for the help!

 

[Tig2575]

An ACTH secreting pituitary tumor is minimally (BUT partially!) responsive to feedback inhibition, so low dose dexa doesn't suppress it's action as it would a normal pituitary, however high dose dexa does.

A primary cortisol producing tumor of the adrenals will have no response to dexa regardless of the dose

 

[Bluefiya]

..

 

[1badvette]

x2 on pathoma ..👍

i had a Q on both the path shelf and the comp i took last week ... make sure u have this down .. goodluck

 

[pathtopenn]

Thanks, Tig that really helps.