Function tests

• Confirmation test of Conn’s syndrome in case of positive aldosterone-renin-ratio

In healthy patients, both volume and sodium-supply suppress renin-secretion, which consequently leads to aldosterone decrease. This does not happen in case of aldosterone-producing adenoma or bilateral hyperplasia of the adrenal cortex.

Aldosterone, renin

2 ml serum and 2 ml EDTA-plasma each, before and after sodium chloride infusion. Freeze samples for shipping by mail.

• Beta-blockers, ACE-inhibitors, AT-1 blockers, thiazide- and loop diuretics can influence the test and should be discontinued 1 week prior to the test.
• Aldosterone receptor antagonists (Spironolactone, eplerenone) and amiloride should be discontinued at least 4 weeks prior to the test.
• Alpha-blockers (such as doxazosin and calcium antagonists (such as amlodipine)) can be used to lower the blood pressure.
• The patient should abstain from liquorice beforehand.
• Prior to carrying out the test, potential hypokalemia must be levelled out and an echocardiography must be done to rule out cardiac insufficiency (Caution: Volume overload!).
• The patient should be empty-stomached and stay empty-stomached throughout the test.
• Due to the higher sensitivity, the test should be performed in a seated position.

1. First blood collection mornings at 8 o’clock prior to sodium chloride-infusion for determination of aldosterone, renin, potassium and sodium.
2. Infusion of 500 ml/hour 0,9 % sodium chloride solution over a period of 4 hours (2 l in total)
3. After 4 hours second blood collection for determination of aldosterone, potassium and sodium.

Side effects:
Caution: Rise in blood pressure, cardiac insufficiency.

Normal findings:
A decrease in aldosterone concentration to < 50 ng/l excludes Conn’s syndrome. Aldosterone levels > 100 ng/l indicate Conn’s syndrome. In between there is a grey area, which requires further diagnostics (for example selective adrenal gland venous catheterization, if necessary with Synacthen stimulation).