Conn’s disease is an endocrine disease:
Pathophysiology
1) inappropriate secretion of aldosterone caused by adrenal adenoma or adrenal hyperplasia 2) type 1 – glucocorticoid suppressible and usually the result of adrenal hyperplasia 2) type 2 – not glucocorticoid suppressible and the result of an adenoma in the adrenal zone fasciculata
Signs and Symptoms of Conn’s disease
1) hypertension (especially diastolic) 2) fatigue and muscle weakness (due to low serum potassium) 3) polyuria 4) polydipsia 5) metabolic alkalosis 6) increased peripheral vascular resistance
Characteristic Test Findings
Laboratory – 1) decreased serum potassium 2) increased serum sodium 3) low plasma renin 4) increased serum aldosterone 5) metabolic alkalosis/increased serum bicarbonate 6) decreases serum magnesium 7) hyperglycemia 8) proteinuria 9) increased serum creatine kinase EKG – 10) premature ventricular contractions 11) prominent U waves
Histology/Gross Pathology
1) small (usually < 3cm; often < 1cm) yellow tumors on gross exam 2) affected adrenal cortex is fasciculata
Associated Conditions
renal failure occurs in 15% of cases
Biochemistry
abnormal hydridization of the 11 beta-hydroxylase gene and the aldosterone synthase gene may have causal role in type 1
Inheritance/Epidemiology
1) some cases of type 1 have autosomal dominant inheritance 2) female to male, 3:1 3) usual age of onset, 30-50 years 4) classically taught that 90% of cases are secondary to adenoma, but incidence of bilateral hyperplasia seems to be increasing 5) one of the five causes of surgically correctable hypertension 6) cause of 1% of hypertension
Treatment
1) type 1 – exogenous glucocorticoids (suppresses corticotropin), aldosterone antagonist (spironolactone, triamterene, amiloride), and sodium restriction 2) type 2 – surgical resection of the adenoma
Tips for USMLE
1) if the patient is not on diuretics, has a low serum potassium that is refractory to replacement, has no limb edema, and has a diastolic blood pressure of 98-100 mmHg, think Conn’s 2) serum aldosterone/plasma renin activity > 30 suggests Conn’s 3) failure of renin to increase with volume depletion suggests Conn’s 4) best way to distinguish between Conn’s (primary aldosteronism) and secondary aldosteronism is there is low renin activity in primary and high renin activity in secondary 5) causes of secondary aldosteronism – congestive heart failure, cirrhosis, and chronic renal failure (kidney is underperfused) 6) if the patient has edema, it is not Conn’s
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