type 4 rta

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96

What is the hallmark electrolyte abnormality of type IV RTA?

Hyperkalemia.

97

Type IV RTA is essentially associated with what hormonal problem?

Hypoaldosteronism or aldosterone resistance.

98

What is unusual about hyperkalemia in type IV RTA?

It may occur without renal failure or be disproportionate to the degree/duration of renal failure.

99

What are the two broad categories of true hypoaldosteronism?

Hyporeninemic hypoaldosteronism and hyperreninemic hypoaldosteronism.

100

Typical pattern in hyporeninemic hypoaldosteronism?

↓ Renin → ↓ Aldosterone.

101

Important causes of hyporeninemic hypoaldosteronism?

NSAIDs, β-blockers, aliskiren, diabetes mellitus/autonomic neuropathy.

102

Typical pattern in hyperreninemic hypoaldosteronism?

↑ Renin → ↓ Aldosterone.

103

Important causes of hyperreninemic hypoaldosteronism?

Primary adrenal insufficiency/Addison disease; ACE inhibitors, ARBs, aldosterone synthase inhibitors.

104

Drugs that inhibit aldosterone synthesis mentioned in the notes?

Heparin and ketoconazole.

105

What is pseudohypoaldosteronism?

Aldosterone resistance despite aldosterone being present.

106

Important acquired causes of pseudohypoaldosteronism?

Chronic tubulointerstitial disease, obstructive nephropathy, calcineurin inhibitors, spironolactone/eplerenone, amiloride/triamterene, trimethoprim, pentamidine.

107

Why can trimethoprim cause hyperkalemia?

It has an amiloride-like effect on ENaC.

108

Why can spironolactone/eplerenone cause hyperkalemia?

Aldosterone receptor blockade → ↓Na⁺ reabsorption and ↓K⁺ secretion.