What is the pathophysiology of secondary 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

Secondary hyperaldosteronism is a collective term for a diverse group of disorders characterized by physiologic activation of the renin-angiotensin-aldosterone (R-A-A) axis as a homeostatic mechanism designed to maintain serum electrolyte concentrations or fluid volume. In the presence of normal renal function, it may lead to hypokalemia.

Secondary hyperaldosteronism can be divided into 2 categories, 1 with associated hypertension and 1 without. The former category includes renovascular hypertension, which results from renal ischemia and hypoperfusion leading to activation of the R-A-A axis. The most common causes of renal artery stenosis in children are fibromuscular hyperplasia and neurofibromatosis. Hypokalemia may occur in as many as 20% of patients.

Plasma renin activity (PRA) levels are often in the reference range, but elevated levels of PRA may be detected after provocation with a single dose of captopril 1 mg/kg. Renal ischemia is also thought to underlie the secondary hyperaldosteronism observed in malignant hypertension.

Hyperreninemia and secondary aldosteronism have also been reported in patients with pheochromocytoma, apparently as a result of functional renal artery stenosis. Renin-producing tumors are very rare, and very high levels of PRA (up to 50 ng/mL/h) are noted, frequently with an increased prorenin-to-renin ratio. The tumors are generally of renal origin and include Wilms tumors and renal cell carcinomas.

Hyperkalemia due to chronic renal failure also causes secondary hyperaldosteronism. Low sodium-to-potassium ratios can be measured in saliva and stool. Cyclosporine-induced hypertension in solid organ transplant patients may also involve a component of hyperaldosteronism.

Secondary hyperaldosteronism in the absence of hypertension occurs as a result of homeostatic attempts to maintain the sodium concentration or circulatory volume or to reduce the potassium concentration. Clinical conditions in which it may arise include diarrhea, excessive sweating, low cardiac output states, and hypoalbuminemia due to liver or renal disease or nephrotic syndrome. Secondary hyperaldosteronism may also occur developmentally in newborn infants (see below).


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