Aldosterone vs. Antidiuretic regulation

[laczlacylaci]

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Hyponatremia introduces low sodium concentration in the blood, yet excessive water retention. How would hormone levels change to reduce these two effects.
Correct answer: Increase aldosterone and decrease ADH

My thoughts:
*Goal: increase Na+ in blood & decrease water retention(absoprtion)/increase water release
1) to decrease water retention/increase water release = decrease ADH.
2) to increase Na+ absorption = increase aldosterone
My concern is that as we increase aldosterone. Na+ comes in, K+ goes out, and water comes in as well. (which is not what we want)

How do we know that the ADH is balancing out the water aldosterone is taking in? (I'm not sure if I'm asking this question correctly)

So, examining the relationship between aldosterone & ADH:
As we increase aldosterone it can -feedback to the posterior pituitary to inhibit release of ADH. Is this true?
If so, it makes sense that in a pt with hyponatremia, as we increase aldosterone->it will decrease ADH.

Is there a way that ADH controls aldoserone? Any other big concept I am missing about these two hormones I need to know for the MCAT?

 

[theonlytycrane]

Great thoughts and approach.

Aldosterone increases sodium reabsorption and water follows by osmosis. The water retention here is much less than the water retained with ADH, so there is likely still a net water loss.

Off the top of my head, I don't know if aldosterone and ADH have interactions, but I wouldn't think so. The former is a steroid hormone and the latter is a peptide. They serve different purposes and are secreted at different places. Think of the hormone feedback systems as separate from one another unless told about an interaction in a passage.

We're told that two things are going on: not enough sodium and too much water. Increasing aldosterone fixes the sodium issue and decreasing ADH fixes the water issue. Keep it as simple as possible for the MCAT 🙂

 

[laczlacylaci]

Your responses are always super helpful! Thanks!