Aldosterone
Sample:
Cold serum or EDTA plasma. The patient has to be either on rest or in activemovement (according to the physician΄s instructions) for at least 30 min before the sampling. Collect 2mL of blood in a plain tube previously immersed in ice. Separate the serum immediately after collection and store frozen at less than -20°C. Hemolysis interferes with the test. Transport frozen the specimen to the laboratory in dry-ice following collection.
Schedule: Friday (RIA)
Units: ng/dL
Range: Upright: 4.0-31ng/dL Supine:1.6 -16 ng/dL
Important: Ratio of Aldosteron/Renin > 50 is critical
Remarks:
Aldosterone is a corticoid hormone released in the adrenal zona glomerulosa under complex control of the Renin/Angiotensin system. Aldosterone stimulates the resorbtion of sodium and water on the distant renal tubule at the expense of increased potassium excretion.
A random measurement of aldosterone is not of diagnostic utility unless Plasma Renin activity is measured simultaneously. The measurement of serum or plasma aldosterone is useful in the diagnosis of primary hyperaldosteronism, which is most commonly caused by an aldosterone- secreting adrenal adenoma (rarely a carcinoma).
About 10-15% of patients have bilateral adrenal hyperplasia and will not respond to adrenalectomy. This can be predicted by measurement of differential adrenal vein aldosterone levels. This condition must be distinguished from secondary hyperaldosteronism, which is common and may be found in association with cirrhosis, renal artery stenosis, renal cysts, nephrotic syndrome, or congestive heart failure.
Primary hyperaldosteronism should be suspected in patients who are hypertensive and hypokalemic. Urine Potassium of less than 30 mEq/24 hrs essentially excludes the diagnosis.
