Step I Q.

[sgsh]

Q. Can anyone give explanation for why there is hypokalemia and metabolic alkalosis in-
1. Gitelman syndrome?
2.Liddle syndrome? ( From : FA, Renal physio)

Thanks.

 

[gleevec1945]

Q. Can anyone give explanation for why there is hypokalemia and metabolic alkalosis in-
1. Gitelman syndrome?
2.Liddle syndrome? ( From : FA, Renal physio)

Thanks.

Gitelman - essentially the same effect as a thiazide diuretic. Leads to increased activity of aldosterone in the collecting duct (increased reabsorption of Na and loss of K and H).
Liddle - hyperactivity of ENaC channel. Essentially like hyperaldosteronism except there will actually be low aldosterone in this patient.

 

[sgsh]

Hi Gleevec, Do u mean to say, thiazide results in increased activity of aldosterone in the collecting duct OR As a defect in Gitelman syndrome, there is increased activity of aldosterone in collecting duct ??? I tried to find about this in Kaplan and first aid but this is not mentioned anywhere. Thanks for trying to clear by doubt.

 

[zhopv10]

The syndrome acts like a thiazide and decreases the function of the sodium channel in the DCT. This leads to increase volume loss, some level of volume contraction and a compensatory response of increased aldosterone.


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[sgsh]

Thanks zhopv10. Gitelman syn. is clear.

Now, Can you/anyone explain by what mechanism Liddle syn results in Metabolic alkalosis and hypokalemia but still decreased aldosterone???

 

[zhopv10]

So it leads to decreased degradation of ENaC's so there are lots of them letting sodium in. This is the mech of aldosterone (or one of them rather) in the collecting duct. So this results in potassium wasting (sodium potassium exchange), increased blood pressure and volume retention/volume expansion. This then leads to low renin (high blood pressure higher perfusion state) which then keeps aldosterone nice and low. So it is pseudoaldosteronism because one of the key mechanisms of aldosterone is to increase ENaC expression but here they are constitutively active.

As for the metabolic alkalosis the hypokalemia is the driving factor I believe: decreased potassium leads to cells letting K out in exchange for H+ coming in, also there is a transcellular shift of potassium (going out) at the proximal tubule resulting in intracellular acidosis which then leads to ammonium production and H+ excretion via that route, and lastly in the presence of hypokalemia H+ secretion in the proximal and distal tubules increases. This leads to further reabsorption of bicarb. Long story short the hypokalemia leads to cellular uptake of H+ ions and increased acid secretion.


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[sgsh]

Thanks zhopv10 for providing detailed explanation.

I found one more explanation which I want to share with u & all.

Liddle is gain of function mutation of ENaC so increased sodium absorbtion in the late dct and ct in expense of K+ and H+, so hypokalemia and met alkalosis.