What is the pathophysiology of primary 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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Answer

The term primary hyperaldosteronism (or primary aldosteronism [PA]) refers to a renin-independent increase in the secretion of aldosterone. This condition is principally a disease of adulthood, with its peak incidence in the fourth to sixth decades of life.

More than 90% of cases of PA are due either to an aldosterone-producing adenoma (APA), which accounts for around 35% of cases (30-40%), or to idiopathic hyperaldosteronism (IHA), which accounts for around 60% of cases (almost all of which are bilateral). Unilateral adrenal hyperplasia (UAH) is a rare cause of PA, accounting for 1-2% of cases. About 1% of patients present with adrenocortical carcinomas that are purely aldosterone-secreting and are usually large at the time of diagnosis; 1% present with familial hyperaldosteronism, and 1% present with an ectopic aldosterone-producing adenoma or carcinoma. [3]

Unilateral adrenal hyperplasia accounts for 14-17% of all cases of unilateral PA. The prevalence of cortical adenoma within cortical hyperplasia is estimated to be 6-24%. The clinical presentation and outcome of patients with unilateral primary hyperaldosteronism are similar regardless of the histopathologic diagnosis. Unilateral adrenocortical hyperplasia is rare. [4]

APAs (sometimes referred to as aldosteronomas) are usually benign encapsulated adenomas that are less than 2 cm in diameter. Most cases are solitary, although in as many as one third of cases, evidence exists of nodularity in the same adrenal gland, suggesting that the condition has arisen in a previously hyperplastic gland.

Patients with IHA have bilateral thickening and variable nodularity of their adrenal cortex. A wide spectrum of severity exists for this disorder, which may go undetected for long periods with no hypokalemia and only mild hypertension. It has been suggested that IHA arises as a result of an undetected adrenal cortex–stimulating factor. Alternatively, the disorder may arise as a result of an activating mutation in an adrenal cortex–specific gene. Neither hypothesis has been proven.

Inherited forms of primary hyperaldosteronism account for only 1% of cases but are more likely to occur during childhood years. These forms include familial hyperaldosteronism (FH) types I, II, and III.


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