Hypoglycemia and ADH

[mrvanda88]

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According to BRS PHYSIO, hypoglycemia increases ADH secretion and I'm stumped as to why that is. I would think that with low blood sugar, if ADH is increased, then wouldn't that decrease blood glucose concentration even further? So why is it that ADH increases when there is hypoglycemia?

 

[SBR249]

Here's my take on it though I'm not sure that it is completely correct. Most of your glucose is reabsorbed in the proximal tubule and that movement of glucose generates a solvent drag that allows a large fraction of filtered water to be reabsorbed as well. When you are hypoglycemic, that solvent drag is reduced, leading to increased volume contraction and the ADH acts to compensate for that so that you don't start losing lots of fluid. ADH is a hormone that acts to defend fluid volume at all cost, including sacrificing plasma osmolarity.

 

[cbrons]

Here's my take on it though I'm not sure that it is completely correct. Most of your glucose is reabsorbed in the proximal tubule and that movement of glucose generates a solvent drag that allows a large fraction of filtered water to be reabsorbed as well. When you are hypoglycemic, that solvent drag is reduced, leading to increased volume contraction and the ADH acts to compensate for that so that you don't start losing lots of fluid. ADH is a hormone that acts to defend fluid volume at all cost, including sacrificing plasma osmolarity.

I think this good. Just one little thing- all glucose (not most) is reabsorbed in the PCT.



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[tarsuc]

hypoglycemia -> inc catecholamines -> inc renin > inc angiotensin II -> inc ADH

doesnt this make more sense?