Aldosterone, Serum

CPT CODE:

USEFUL FOR:

Investigation of primary aldosteronism (eg, adrenal adenoma/carcinoma and adrenal cortical hyperplasia) and secondary aldosteronism (renovascular disease, salt depletion, potassium loading, cardiac failure with ascites, pregnancy, Bartter's syndrome).

SPECIMEN REQUIRED:

Draw blood in a plain, red-top tube(s) at 8 a.m. Spin down and send 1.2 mL of serum frozen in plastic vial. See "Renin - Aldosterone Studies" in Special Instructions for more detailed instructions.Note:     If ordered with #8060 "Renin Activity, Plasma," plasma is                   acceptable. See #8060 "Renin Activity, Plasma" for                   specimen required.

TRANSPORT TEMPERATURE:

Frozen\Refrig OK\Ambient OK

CLINICAL INFORMATION:

Aldosterone stimulates sodium transport across cell membranes, particularly in the distal renal tubule where sodium is exchanged for hydrogen and potassium. Secondarily, aldosterone is important in the maintenance of blood pressure and blood volume.
Aldosterone is the major mineralocorticoid and is produced by the adrenal cortex.
The renin-angiotensin system is the primary regulator of the synthesis and secretion of aldosterone. Likewise, increased concentrations of potassium in the plasma may directly stimulate adrenal production of the hormone. Under physiologic conditions, pituitary adrenocorticotropic hormone is not a major factor in regulating aldosterone secretion.

CLINICAL INTERPRETATION:

A high ratio of serum aldosterone (SA) in ng/dL to plasma renin activity (PRA) in ng/mL per hour, is a positive screening test result, a finding that warrants further testing. A SA/PRA ratio > or = 20 is only interpretable with a SA > or = 15 ng/dL and indicates probable primary aldosteronism.  
Renal disease, such as unilateral renal artery stenosis, results in elevated renin and aldosterone levels. Renal venous catheterization may be helpful. A positive test is a renal venous renin ratio (affected/normal) >1.5.
See "Renin - Aldosterone Studies" under Special Instructions
Note:      Advice on stimulation or suppression tests is available                   from Mayo Clinic's Division of Endocrinology and may                   be obtained by calling Mayo Medical Laboratories.

REFERENCE VALUES:

0-30 days:  17-154 ng/dL *

1-11 months:  6.5-86 ng/dL *

1-10 years:  <=40 ng/dL (supine) *

                        <=124 ng/dL (upright) *

> or = 11 years:  <=21 ng/dL (a.m. peripheral vein specimen)

Reference range based on upright a.m. collection from

subjects on ad lib sodium intake.

*Loeuille GA, Racadot A, Vasseur P, Vandewalle B:  Blood

and urinary aldosterone levels in normal neonates, infants

and children. Pediatrie 1981;36:335-344