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Posture Studies

The principle here is that the adrenal adenomas producing aldosterone are sensitive to ACTH whereas bilateral idiopathic adrenal hyperplasia is sensitive to angiotensin II. Patients have blood tests at 0800 for aldosterone, cortisol and renin after sleeping all night. After 4 hours of being upright and walking around (which stimulates angiotensin II production due to blood pressure changes, not affecting ACTH) the blood tests are repeated. Adrenal adenomas will show very little change in aldosterone levels whereas the benign adrenal hyperplasia cases will show increased aldosterone (due to stimulation by the increased angiotensin II.)