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Primary hyperaldosteronism
Classification and external resources

Aldosterone
ICD-10 E26.0
ICD-9 255.1
DiseasesDB 3073
MedlinePlus 000330
eMedicine med/432
MeSH D006929

Primary aldosteronism, also known as primary hyperaldosteronism, is characterized by the overproduction of the mineralocorticoid hormone aldosterone by the adrenal glands.[1] Aldosterone causes increase in sodium and water retention and potassium excretion in the kidneys, leading to arterial hypertension (high blood pressure). An increase in the production of mineralocorticoid from the adrenal gland is evident. It is the most common cause of secondary hypertension [2].

Primary hyperaldosteronism has many causes, including adrenal hyperplasia and adrenal carcinoma.[3] When it occurs due to a solitary aldosterone-secreting adrenal adenoma (a type of benign tumor), it is known as Conn's syndrome.[4] In practice, however, the two terms are often used interchangeably, regardless of the underlying physiology.

Contents

Causes

The syndrome is due to:

Signs, symptoms and findings

Aldosterone enhances exchange of sodium for potassium in the kidney so increased aldosteronism will lead to hypernatremia and hypokalemia. Once the potassium has been significantly reduced by aldosterone, a sodium/hydrogen pump in the nephron becomes more active leading to increased excretion of hydrogen ions and further exacerbating the hypernatremia. The hydrogen ions that are exchanged for sodium are generated by carbonic anhydrase in the renal tubule epithelium causing increased production of bicarbonate. The increased bicarbonate and the excreted hydrogen combine to generate a metabolic alkalosis. The sodium retention leads to plasma volume expansion and elevated blood pressure. The increased blood pressure will lead to increased glomerular filtration rate and cause a decrease in renin release from the peritubular capillary epithelium in the kidney. If there is a primary hyperaldosteronism the decreased renin (and subsequent decreased angiotensin II) will not lead to a decrease in aldosterone levels (a very helpful clinical tool in diagnosis of primary hyperaldosteronism). Aside from high blood pressure manifestations of muscle cramps (due to hyperexcitability of neurons secondary to hypocalcemia), muscle weakness (due to hypoexcitability of skeletal muscles secondary to hypokalemia), and headaches (due to the low potassium or high blood pressure) may be seen. The high pH of the blood makes calcium less available to the tissues and causes symptoms of hypocalcemia (low calcium levels).

Secondary hyperaldosteronism is often related to decreased cardiac output which is associated with elevated renin levels.

Diagnosis

Measuring aldosterone alone is not considered adequate to diagnose primary hyperaldosteronism. Rather, both renin and aldosterone are measured, and the ratio is diagnostic.[5][6]

Usually, renin levels are suppressed, leading to a very low renin-aldosterone ratio (<0.0005). This test is confounded by antihypertensive drugs, which have to be stopped up to 6 weeks.

If plasma levels of renin and aldosterone suggest hyperaldosteronism, CT scanning can confirm the presence of an adrenal adenoma. If the clinical presentation primarily involves hypertension and elevated levels of catecholamines, CT or MRI scanning can confirm a tumor on the adrenal medulla, typically a pheochromocytoma.

Hyperaldosteronism can be mimicked by Liddle syndrome, and by ingestion of licorice and other foods containing glycyrrhizin. In one case report, hypertension and quadriparesis resulted from intoxication with a non-alcoholic pastis (an anise-flavored aperitif containing glycyrrhizinic acid).[7]

Therapy

The treatment for hyperaldosteronism depends on the underlying cause. In patients with a single benign tumor (adenoma), surgical removal (adrenalectomy) is curative. This is usually performed laparoscopically, through several very small incisions. For patients with hyperplasia of both glands, successful treatment is often achieved with spironolactone or eplerenone, drugs that block the effect of aldosterone. In males, one common side effect of spironolactone drug therapy sometimes seen is gynecomastia. Gynecomastia usually does not occur with eplerenone drug therapy.

In the absence of proper treatment, individuals with hyperaldosteronism often suffer from poorly controlled high blood pressure, which may be associated with increased rates of stroke, heart disease, and kidney failure. With appropriate treatment, the prognosis is excellent.[8]

Eponym

Conn's syndrome is named after Jerome W. Conn (1907–1994), the American endocrinologist who first described the condition at the University of Michigan in 1955.[1]

References

  1. ^ a b Conn JW, Louis LH (1955). "Primary aldosteronism: a new clinical entity". Trans. Assoc. Am. Physicians 68: 215–31; discussion, 231–3. PMID 13299331.  
  2. ^ http://emedicine.medscape.com/article/117280-overview
  3. ^ http://www.merck.com/mmhe/sec13/ch164/ch164e.html
  4. ^ Cotran, Ramzi S.; Kumar, Vinay; Fausto, Nelson; Nelso Fausto; Robbins, Stanley L.; Abbas, Abul K. (2005). Robbins and Cotran pathologic basis of disease. St. Louis, Mo: Elsevier Saunders. pp. 1210. ISBN 0-7216-0187-1.  
  5. ^ Tiu S, Choi C, Shek C, Ng Y, Chan F, Ng C, Kong A (2005). "The use of aldosterone-renin ratio as a diagnostic test for primary hyperaldosteronism and its test characteristics under different conditions of blood sampling". J Clin Endocrinol Metab 90 (1): 72–8. doi:10.1210/jc.2004-1149. PMID 15483077.  
  6. ^ United Bristol Healthcare NHS Trust, the major teaching trust in South West England
  7. ^ Trono D, Cereda JM, Favre L (August 1983). "[Pseudo-Conn's syndrome due to intoxication with nonalcoholic pastis]" (in French). Schweiz Med Wochenschr 113 (31-32): 1092–5. PMID 6623028.  
  8. ^ Columbia Adrenal Center, Hyperaldosteronism (Conn's Syndrome)
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