How is syndrome of apparent mineralocorticoid excess differentiated from hyperaldosteronism?

Updated: Oct 19, 2018
  • Author: George P Chrousos, MD, FAAP, MACP, MACE, FRCP(London); Chief Editor: Robert P Hoffman, MD  more...
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Syndrome of apparent mineralocorticoid excess

The syndrome of apparent mineralocorticoid excess is a rare cause of juvenile hypertension that was first described in 1979; since then, an additional 25-30 cases have been reported. Patients present with severe hypokalemia and metabolic alkalosis and suppressed plasma renin activity (PRA) and aldosterone levels. Two types of apparent mineralocorticoid excess have been described.

Type I apparent mineralocorticoid excess is characterized by impaired 11β-hydroxysteroid dehydrogenase (11β-HSD) activity with impaired conversion of cortisol to cortisone and impaired 5β-reductase activity. These patients have markedly elevated urinary ratios of cortisol, tetrahydrocortisol (THF), and allo-THF to cortisone, tetrahydrocortisone (THE), and allo-THE. Many of these patients have molecular defects of 11β-HSD type 2 (11β-HSD2).

Type II apparent mineralocorticoid excess is characterized by a decreased rate of cortisol clearance and turnover but a normal urinary THF-to-THE ratio.

Treatment of apparent mineralocorticoid excess is often difficult. A low-sodium diet in conjunction with spironolactone 1-4 mg/kg/day is often effective but may not yield long-lasting results. Patients with type II apparent mineralocorticoid excess respond to suppression of cortisol production with dexamethasone, a steroid with little mineralocorticoid activity. The problem is that dexamethasone has its significant growth-suppressing properties and therefore is not suitable for growing children.

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