PA Has Various Subtypes

Two major forms of primary aldosteronism account for 95% of cases while the remaining 5% are associated with five other types of the disease.

Most Common Forms of Primary Aldosteronism

Bilateral Adrenal Hyperplasia (BAH). BAH affects both adrenal glands, and accounts for about 60% of all cases. In this form of PA, also called Idiopathic Adrenal Hyperplasia (IAH), both adrenal glands produce excess aldosterone in a fairly similar way. On a computed tomography imaging (CT scan), the adrenal cortex may have a bumpy appearance, perhaps caused by separate clusters of aldosterone-producing cells (APCC) or the adrenal glands may appear normal.

Aldosterone Producing Adenoma (APA). APA is due to a benign tumor on the adrenal gland. Often small, adrenal lesions linked to APA are typically <2 cm in diameter, and are the cause of the excess aldosterone. About 35% of PA cases are due to an APA.

Primary Aldosteronism Subtypes

Source: “Changes in the perceived epidemiology of primary hyperaldosteronism” Int J Hypertens. 2011;2011:162804.

Less Common Forms of Primary Aldosteronism

Unilateral Adrenal Hyperplasia (UAH). UAH is often difficult to distinguish from an APA, in part, because it also affects a single gland. Like bilateral disease, it may also be caused by separate aldosterone-producing cell clusters that appear as micronodules on a CT scan of the adrenal gland or the adrenal gland may appear normal on CT. Oftentimes, it is not diagnosed until after an adrenal gland has been removed, and the gland is reviewed under a microscope by the pathologist.

Familial Forms. Five recognized forms of hyperaldosteronism are caused by genetic variations which run in families. These inherited forms of primary aldosteronism are typically apparent early in life, when small children or juveniles develop severe hypertension or hypokalemia. Milder forms may sometimes go unnoticed until adulthood:

  • The most well-known form of familial PA is FH-1 or Glucocorticoid Remedial Aldosteronism (GRA). It accounts for about 1% of all people with PA.
  • FH-2 is more common (i.e., it may account for as many as 7% of PA cases), but can only be investigated through genetic testing.
  • FH-3 includes two different subtypes. Type A manifests as a severe form that leads to severe drug-resistant hypertension and hypokalemia in early childhood. Type B is a milder form that may not be apparent until early adulthood, and is treatable through medications.
  • FH-4 and FH-5 have only been confirmed in a very limited number of cases.

Adrenocortical Carcinoma. Cancer of the adrenal cortex is an extremely rare cause of PA that affects about 1 in a million people in the US. Unlike benign adenomas, these tumors grow very quickly and tend to be much larger (> 4 cm) when discovered.

Ectopic Aldosterone-Producing Tumors. Sometimes excess aldosterone can be produced outside of the adrenal glands by a tumor located on another organ. These cases are extremely rare and difficult to detect. They account for <0.1% of all confirmed cases.

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