step1mom
Forum Senior
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is it the weak mineralocorticoid that controls bp or aldosterone?
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| mildus
Forum Guru
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I think that aldosteron is the most important
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| GMOB
Forum Elite
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aldosterone is the main mineralocorticoid under normal conditions, and it maintains BP. When there is an abnormality, like an inborn error of metabolism and any of the enzymes get affected on the adrenal cortex synthesis, you will get a decrease of BP, but only on 21bhydroxylase def. because ALL mineralocorticoid will deficient. But in blockage of 11 b hydroxylase or 17 alfa hydroxylase you will get a RISE in BP because there is weak mineralocorticod activity enhanced (11-deoxycorticosterone). Whenever there is an enzyme def. there is a def. in cortisol, so you will lose neg. feedback to ACTH, it will start firing, which will stimulate overproduction of everything above the blockage. That is why, in abnormal situations, ACTH is the one driving the BP up, except in 21b hydrox. def.
Hope this helps! 
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| mildus
Forum Guru
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Thanks GMOB, it is nice explanation
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| GMOB
Forum Elite
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I'm actually ashamed to admitt i NEVER EVER understood this, not even through med school! just now, it all makes sense...I am using Kap. letures...My exam is in a couple of weeks, so i better learn all this s***! 
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| mildus
Forum Guru
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Good luck on your exam
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| GMOB
Forum Elite
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One added note, on 17alfa def. there is increase of both 11-deoxycorticosterone and ALDOSTERONE (initially)! everything above the blockade will increase, including internediates and the end products, therefore, Aldosterone increases in 17 alfa def. For some reason, in my kaplan physio notes, on chart IX-3-1 it shows Aldosterone secretion on 17 alfa def. as decreasing, i'm thinking that since BP is high due to excess weak mineralocorticoid, then AII will shut down, and therefore Aldosterone will decrease too. And high BP is maintained by excess mineralocorticoid. In other books it shows Aldosterone as increasing (Physio BRS) but i think it only increases until AII shuts down. What do you guys think?
Edited by GMOB on 10/19/05 - 12:43 PM. Reason: corrections
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