bluestar
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Since in addison's disease there's hyperpigmentation caused by decreased feedback inhibition of ACTH by cotisol then is there hyperpigmentation in Cushing's disease as well (since ACTH is also high)?
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| mani
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i think any condition with increased pituitary ACTH cn leand to hyperpigmentation, but not ectopic ACTH.
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| mash
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hyperpigmentation in cushings or any other condition causing increased ACTH is due to melanocyte stimulating sequence within ACTH molecule
so, i think ectopic ACTH shud cause hyperpigmentation too.
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| mani
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i thought preopiomelanocoticitropin is synthesized only in pituitary
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| mash
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of course it is produced in ant pit only but proopiomelanocortin produces two forms of MSH in addition to being a precursor of ACTH. One of them, α-MSH, is identical to the first 13 amino acids at the amino terminal of ACTH.
and hyperpigmentation occurs as a result of the action of ACTH on cutaneous MSH receptors.
so, whether it is ectopic or due to pit adenoma, inc ACTH is going to cause hyperpigmentation...
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| Idiopathic
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This is assuming that ectopic ACTH is exactly like endogenous ACTH, which may not be true. Remember, the PTH that is secreted in some cacncers (renal, lung), is actually PTrP, which is not identical to PTH and does not show up on a PTH serum assay. While ectopic ACTH will show up on a test, it may not have exactly the same properties as pituitary ACTH. With that in mind, the clinical picture between Cushing's and Addison's is markedly different and one should never be confused for the other.
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| bluestar
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Idiopathic, thanks for replying. but I don't get your point. In Cushing's disease, the production of ACTH is not ectopic, then why did you say " the clinical picture between Cushing's and Addison's is markedly different and one should never be confused for the other."?
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| bluestar
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Idiopathic, thanks for replying. but I don't get your point. In Cushing's disease, the production of ACTH is not ectopic, then why did you say " the clinical picture between Cushing's and Addison's is markedly different and one should never be confused for the other."?
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| Idiopathic
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THe original question asked about hyperpigmentation in Cushings and how to differentiate. You should never have to differentiate Cushings vs Addisons on pigmentation, since they are so different clinically. CUshings disease/syndrome CAN be ectopic in origin and I cannot guarantee that you would or wouldnt get hyperpigmentation with this disorder. It has been seen but that doesnt mean it would or wouldnt be there,
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| bluestar
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OK.
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