Clinical Significance

Renin and aldosterone measurements are used in the investigation of patients with suspected:

Primary hyperaldosteronism (PA, Conn’s syndrome) is a disorder caused by excessive secretion of aldosterone by the adrenal gland, where high levels of circulating aldosterone are expected in the presence of low renin concentration or low plasmatic renin activity levels. Such inappropriately high aldosterone production (non-suppressible by sodium loading) causes cardiovascular damage, suppression of plasma renin, hypertension, sodium retention and potassium excretion that, if prolonged and severe, may lead to hypokalemia. The major causes of PA (>90% cases) are adrenal adenoma and unilateral or bilateral adrenal hyperplasia. Rare cases are due to the inherited condition of glucocorticoidremediable aldosteronism.

Secondary hyperaldosteronism is caused by disorders that activate the renin-angiotensin-aldosterone axis, resulting in excessive production of aldosterone (renovascular disease, salt depletion, potassium loading, cardiac failure with ascites, pregnancy, Bartter’s syndrome).

Hypoaldosteronism is a rare condition often due to primary adrenal failure, where plasma aldosterone has low concentrations in the presence of high concentrations of plasma renin. In hypoaldosteronism caused by low secretion of renin, low levels of plasma renin are expected in the presence of low levels of plasma aldosterone

Since plasma aldosterone shows typical bursts, which follow a circadian rhythm, it might not be advisable to draw conclusions from a single determination. Plasma aldosterone measurement is used for acute studies (like circadian rhythms, postural changes, acute effect of drugs), the 24-hour urinary measurement helps determine the relationship between sodium excretion and aldosterone levels and may also be used to help to rule out high aldosterone secretion as a cause of another condition.