Aldosteronism

Aldosteronism

 

Aldosteronism is a syndrome caused by excessive and inappropriate aldosterone production.

Epidemiology

  • Prevalence – 5-15% of unselected hypertensive patients
  • Age – 30-50 years
  • Sex – F:M is 2:1

Etiologies

  • Bilateral cortical nodular hyperplasia
  • Aldosterone-producing tumor (Conn’s Syndrome)
  • Adrenal carcinoma, rare in the general population

Pathophysiology

  • Hypersecretion of aldosterone increases the renal distal tubular exchange of sodium for potassium and hydrogen
  • Progressive depletion of potassium and hydrogen leads to hypokalemia and acidosis
  • Excess sodium reabsorption leads to hypertension
  • Classification
    • Primary – excess aldosterone secretion by the adrenal glands
    • Secondary – renin-mediated secretion
      • Seen in congestive heart failure, nephritic syndrome, cirrhosis, renal artery hypertension, severe arteriolar nephrosclerosis, rare renin-secreting tumors

Clinical Presentation

  • Constitutional – weakness, fatigue
  • Renal – polyuria, proteinuria, renal failure
  • Cardiac – hypertension, cardiac hypertrophy
  • Edema – rarely exists

Diagnosis

  • Indications for testing
    • Suggested by persistent hypokalemia and hypertension in patients with normal sodium intake, absence of edema and not currently receiving diuretics (from electrolyte testing)
      • Hypokalemia – often severe; although patients may have normokalemia, particularly if already taking potassium-sparing diuretics
      • Impaired urinary concentration
      • Metabolic alkalosis
      • Hypomagnesemia if hypokalemia is severe
      • Hypernatremia is rare
    • Patients may only present with hypertension and be normokalemic
  • Laboratory testing
    • Screening – upright Aldosterone: renin activity ratio, or upright aldosterone:direct renin ratio
    • Confirmation
      • Fludrocortisone suppression test
      • Saline loading test
      • Saline infusion test
      • Captopril test
      • Losartan suppression test
  • Imaging studies
    • Adrenal MRI or CT to screen for tumor

Treatment

  • Often involves surgical excision of the tumor
  • Aldosterone antagonists (spironolactone) may be successful therapy