1st order laboratory parameters – obligatory laboratory tests.
- Aldosterone, renin
- Serum aldosterone–renin ratio (ARR) [> 200] Caution. Various drugs (eg, ACE inhibitors, sartans, beta-blockers, potassium-sparing diuretics) affect the result and must be discontinued 2 weeks before (see under: “Serum aldosterone renin quotient”)Note: Blood collection ideally in the morning at least two hours before getting up; the patient should sit for 5 to 15 minutes beforehand.
- Electrolytes (blood salts) – sodium, potassium.
- Blood gas analysis (BGA)
Laboratory parameters 2nd order – depending on the results of the history, physical examination and mandatory laboratory parameters – for differential diagnostic clarification.
- Tetrahydroaldosterone in 24 h collection urine.
- Confirmatory tests
- Saline load test
- Oral saline load test – In healthy individuals, adrenal cortex aldosterone production normally decreases after saline intake [primary hyperaldosteronism: aldosterone production is inadequately suppressed or not suppressed at all].
- Intravenous saline load test
Note: The saline load test in the sitting position is more sensitive than in the supine position and has a low rate of false positive and equivocal results.
- Fludrocortisone suppression test (reference test).
- Captopril loading test
- Saline load test
- Renin-aldosterone orthostasis test – for suspected (V. a.) aldosterone-producing adenoma.
- 18-0H-cortisol and molecular genetic analysis – in V. a. glucocorticoid-suppressible primary hyperaldosteronism (GSH; synonym: dexamethasone-suppressible hyperaldosteronism, glucocorticoid-remediable aldosteronism, GRA).
Further notes
- In primary hyperaldosteronism (Conn syndrome), the adrenal cortex produces increased aldosterone without activation by the renin-angiotensin-aldosterone system (RAAS): serum aldosterone-renin ratio (ARR) [> 200].
- In secondary hyperaldosteronism, the adrenal cortex produces increased aldosterone through chronic activation of the renin-angiotensin-aldosterone system (RAAS), i.e., both aldosterone and renin are elevated, so the serum aldosterone-renin ratio is normal.
