ALDOSTERONE, LC/MS/MS

ALDOSTERONE

Aldosterone is a hormone that plays an important role in maintaining normal sodium and potassium concentrations in blood and in controlling blood volume and blood pressure. Renin is an enzyme that controls aldosterone production. These tests measure the levels of aldosterone and renin in the blood and/or the level of aldosterone in urine.

Aldosterone is produced by the adrenal glands located at the top of each kidney, in their outer portion (called the adrenal cortex). Aldosterone stimulates the retention of sodium (salt) and the elimination of potassium by the kidneys. Renin is produced by the kidneys and controls the activation of the hormone angiotensin, which stimulates the adrenal glands to produce aldosterone.

The kidneys release renin when there is a drop in blood pressure or a decrease in sodium chloride concentration in the tubules in the kidney. Renin cleaves the blood protein angiotensinogen to form angiotensin I, which is then converted by a second enzyme to angiotensin II. Angiotensin II causes blood vessels to constrict, and it stimulates aldosterone production. Overall, this raises blood pressure and keeps sodium and potassium at normal levels.

A variety of conditions can lead to aldosterone overproduction (hyperaldosteronism, usually just called aldosteronism) or underproduction (hypoaldosteronism). Since renin and aldosterone are so closely related, both substances are often tested together to identify the cause of an abnormal aldosterone.