Conn's syndrome: Difference between revisions
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The syndrome is due to: |
The syndrome is due to: |
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* Bilateral (micronodular) adrenal hyperplasia, 60% |
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* Adrenal (Conn's) [[adrenal adenoma |adenoma]], 40% |
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* Glucocorticoid-remediable hyperaldosteronism ([[dexamethasone]]-suppressible hyperaldosteronism), <1% |
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* [[aldosterone]]-secreting [[adrenal adenoma]] (benign tumor, < 5%) |
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* rare forms, including disorders of the [[renin-angiotensin system]] |
* rare forms, including disorders of the [[renin-angiotensin system]], <1%<ref> Longo, Dan L et al (2012). Harrison's Principals of Internal Medicine, Vol. 2. New York: McGraw-Hill. p. 2949. ISBN 978-0-07-174887-2.</ref> |
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==Pathogenesis== |
==Pathogenesis== |
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Revision as of 15:47, 8 February 2013
| Conn's syndrome |
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Conn's syndrome is an aldosterone-producing adenoma. 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]
Causes
Primary hyperaldosteronism has many causes, including adrenal hyperplasia and adrenal carcinoma.[2]
The syndrome is due to:
- Bilateral (micronodular) adrenal hyperplasia, 60%
- Adrenal (Conn's) adenoma, 40%
- Glucocorticoid-remediable hyperaldosteronism (dexamethasone-suppressible hyperaldosteronism), <1%
- rare forms, including disorders of the renin-angiotensin system, <1%[3]
Pathogenesis
Aldosterone enhances exchange of sodium for potassium in the kidney, so increased aldosteronism will lead to hypernatremia (elevated sodium level) and hypokalemia (low blood potassium). 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 elevated sodium level resulting in a further increase in hypernatremia. The hydrogen ions 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 high pH of the blood makes calcium less available to the tissues and causes symptoms of hypocalcemia (low calcium levels).
The sodium retention leads to plasma volume expansion and elevated blood pressure. The increased blood pressure will lead to an increased glomerular filtration rate and cause a decrease in renin release from the granular cells of the juxtaglomerular apparatus in the kidney. If a patient is thought to suffer from primary hyperaldosteronism, the aldosterone:renin activity ratio is used to assess this. The decreased renin levels and in turn the reactive down-regulation of angiotensin II are thought to be unable to down-regulate the constitutively formed aldosterone, thus leading to an elevated [plasma aldosterone:plasma renin activity] ratio (lending the assay to be a clinical tool for diagnostic purposes).
Aside from hypertension, other manifesting problems include myalgias, weakness, and chronic headaches. The muscle cramps are due to neuron hyperexcitability seen in the setting of hypocalcemia, muscle weakness secondary to hypoexcitability of skeletal muscles in the setting of low blood potassium (hypokalemia), and headaches which are thought to be due to both electrolyte imbalance (hypokalemia) and hypertension.
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. The screening test of choice for diagnosis is the plasma aldosterone:plasma renin activity ratio. Renin activity, not simply plasma renin level, is assayed. Both renin and aldosterone are measured, and a ratio greater than 30 is indicative of primary hyperaldosteronism.[4][5]
Differential diagnosis
Hyperaldosteronism can be mimicked by Liddle syndrome, and by ingestion of liquorice and other foods containing glycyrrhizin. In one case report, hypertension and quadriparesis resulted from intoxication with a nonalcoholic pastis (an anise-flavored aperitif containing glycyrrhizinic acid).[6]
Therapy
In patients with a single benign tumor (adenoma), surgical removal (adrenalectomy) may be 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.[citation needed]
Prognosis
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.[7]
See also
References
- ^ Conn JW, Louis LH (1955). "Primary aldosteronism: a new clinical entity". Trans. Assoc. Am. Physicians. 68: 215–31, discussion, 231–3. PMID 13299331.
- ^ http://www.merck.com/mmhe/sec13/ch164/ch164e.html
- ^ Longo, Dan L et al (2012). Harrison's Principals of Internal Medicine, Vol. 2. New York: McGraw-Hill. p. 2949. ISBN 978-0-07-174887-2.
- ^ 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.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ United Bristol Healthcare NHS Trust, the major teaching trust in South West England
- ^ Trono D, Cereda JM, Favre L (1983). "[Pseudo-Conn's syndrome due to intoxication with nonalcoholic pastis]". Schweiz Med Wochenschr (in French). 113 (31–32): 1092–5. PMID 6623028.
{{cite journal}}: Unknown parameter|month=ignored (help)CS1 maint: multiple names: authors list (link) - ^ Columbia Adrenal Center, Hyperaldosteronism (Conn's Syndrome)
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