Hyperaldosteronism

• Excess production of aldosterone independent of the renin-angiotensin system causing increased sodium and water retention and reduced renin release
• Associated with hypertension, hypokalaemia or alkalosis
• Sodium tends to be normal or slightly raised

Symptoms

• Generally asymptomatic
• May present with features of hypokalaemia;
• Weakness, cramps, parasthesia, polyuria and polydipsia

Causes

• 2/3 due to a solitary aldosterone secreting adenoma (Conn’s syndrome)
• 1/3 are due to bilateral adrenocortical hyperplasia
• Rare causes;
  • Adrenal carcinoma
  • Glucocorticoid-remediable aldosteronism (GRA) – when the ACTH regulatory element of the 11?-hydroxylase gene fuses to the aldosterone synthase gene increasing aldosterone production and bringing it under the control of ACTH

Investigations

• U&E’s ideally after being off diuretics, hypotensives, steroids or laxatives for 4 weeks
• Aldosterone/renin ratio (ARR)
  • Measured when the patient has been upright or sitting for 2hr as posture affects results
  • A raised ratio indicated hyperaldosteronism
• Assess the effects of posture
  • Renin, aldosterone and cortisol are measured after the patient has been lying overnight then repeated up being upright for 4hr
  • Renin production increases on standing, causing increased aldosterone production
  • This is exaggerated in bilateral hyperplasia but there is no effect in Conn’s as aldosterone production is autonomous
• CT/MRI adrenals
  • Trial of glucocorticoids is GA is suspected (dexamethasone causes decreased ACTH production by negative feedback and therefore reduced aldosterone production

Treatment

• Conn’s – surgery. Spironolactone is used for 4wk prior to surgery to reduce hypertension and to treat low K+
• Hyperplasia – treat medically spironolactone or amiloride
• GRA – dexamethasone for 4wk generally normalises biochemistry and spironolactone to reduced BP

Secondary hyperaldosteronism

• Due to high renin from reduced renal perfusion e.g. renal artery stenosis, accelerated hypertension, diuretics, CCF or hepatic failure