Primary hyperaldosteronism was previously thought to be most commonly caused by an adrenal adenoma, termed Conn's syndrome. However, recent studies have shown that bilateral idiopathic adrenal hyperplasia is the cause in up to 70% of cases. Differentiating between the two is important as this determines treatment. Adrenal carcinoma is an extremely rare cause of primary hyperaldosteronism.


  • Incidence: 40.00 cases per 100,000 person-years
  • Peak incidence: 40-50 years
  • Sex ratio: 1:1
<1 1-5 6+ 16+ 30+ 40+ 50+ 60+ 70+ 80+

Clinical features



  • the 2016 Endocrine Society recommend that a plasma aldosterone/renin ratio is the first-line investigation in suspected primary hyperaldosteronism
    • should show high aldosterone levels alongside low renin levels (negative feedback due to sodium retention from aldosterone)
  • following this a high-resolution CT abdomen and adrenal vein sampling is used to differentiate between unilateral and bilateral sources of aldosterone excess
  • Adrenal Venous Sampling (AVS) can be done to identify the gland secreting excess hormone in primary hyperaldosteronism


  • adrenal adenoma: surgery
  • bilateral adrenocortical hyperplasia: aldosterone antagonist e.g. spironolactone