NeimanPicksMOM
Topics: 5
Posts: 24
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Hey guys.
Does anyone know why during a dexamethasone suppression test, in the presence of an ACTH tumor, cortisol increases after a low dose and decreases after a high dose?
It's not clicking in my head,
also, quickly, what is the difference between Alkaline Phospatase and Phosphorus? FA says that in hyperparathyroidism Phosp decreases while alkaline phosphatase increases.
THANKS hope these q's help u guys too!
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| me007
Forum Guru
Topics: 72
Posts: 803
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let's try
No Cushing -- normal cortisol level -- normal ACTH
+dexametason --> lower ACTH -->lowering own cirtisol
adrenal Cushing -- hight cortisol -- low ACTH
+dexam (low or high) --higher corticosteroid level --> ACTH low anyway
pituitary Cushing --> high cortisol - high ACTH
+dexam low dose --> higher corticosteroid - high ACTH (pituitary doesn't feel difference)
+high dose dexam --> much higher corticost level --> lower ACTH (pituit can feel this difference)
Supressed pituitary in adrenal Cushing not responding to whatever level of corticosteroids
and not supressed but not sensitive to average fluctuation of cortisol level in pituitary Cushing - respond to high dexam but not to low dose
Is it ok?
Edited by me007 on 02/08/07 - 12:09 PM
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| NeimanPicksMOM
Topics: 5
Posts: 24
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YES I UNDERSTAND thank you. 
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| mildus
Forum Guru
Topics: 19
Posts: 614
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excellent explanation me007
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| SmokyWaters
Forum Elite
Topics: 6
Posts: 458
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me007 gave very good explanation that pituitary cant feel the difference. The reason why it cant feel the difference is unknown ...but after a few studies it was found that a low dose level causes no change while the high dose causes it....
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