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Chapter 046. Sodium and Water (Part 17)

Decreased aldosterone synthesis may be due to primary adrenal insufficiency (Addison's disease) or congenital adrenal enzyme deficiency (Chap. 336). Heparin (including low-molecular-weight heparin) inhibits production of aldosterone by the cells of the zona glomerulosa and can lead to severe hyperkalemia in a subset of patients with underlying renal disease, diabetes mellitus, or those receiving K+-sparing diuretics, ACE inhibitors, or NSAIDs. Pseudohypoaldosteronism is a rare familial disorder characterized by hyperkalemia, metabolic acidosis, renal Na+ wasting, hypotension, high renin and aldosterone levels, and end-organ resistance to aldosterone. . | Chapter 046. Sodium and Water Part 17 Decreased aldosterone synthesis may be due to primary adrenal insufficiency Addison s disease or congenital adrenal enzyme deficiency Chap. 336 . Heparin including low-molecular-weight heparin inhibits production of aldosterone by the cells of the zona glomerulosa and can lead to severe hyperkalemia in a subset of patients with underlying renal disease diabetes mellitus or those receiving K -sparing diuretics ACE inhibitors or NSAIDs. Pseudohypoaldosteronism is a rare familial disorder characterized by hyperkalemia metabolic acidosis renal Na wasting hypotension high renin and aldosterone levels and end-organ resistance to aldosterone. The gene encoding the mineralocorticoid receptor is normal in these patients and the electrolyte abnormalities can be reversed with suprapharmacologic doses of an exogenous mineralocorticoid e.g. 9a-fludrocortisone or an inhibitor of 110-HSDH e.g. carbenoxolone . The kaliuretic response to aldosterone is impaired by K -sparing diuretics. Spironolactone is a competitive mineralocorticoid antagonist whereas amiloride and triamterene block the apical Na channel of the principal cell. Two other drugs that impair K secretion by blocking distal nephron Na reabsorption are trimethoprim and pentamidine. These antimicrobial agents may contribute to the hyperkalemia often seen in patients infected with HIV who are being treated for Pneumocystis carinii pneumonia. Hyperkalemia frequently complicates acute oliguric renal failure due to increased K release from cells acidosis catabolism and decreased excretion. Increased distal flow rate and K secretion per nephron compensate for decreased renal mass in chronic renal insufficiency. However these adaptive mechanisms eventually fail to maintain K balance when the GFR falls below 10-15 mL min or oliguria ensues. Otherwise asymptomatic urinary tract obstruction is an often overlooked cause of hyperkalemia. Other nephropathies associated with impaired K excretion