How is postural testing performed in the workup of primary hyperaldosteronism?

Updated: Oct 19, 2018
  • Author: George P Chrousos, MD, FAAP, MACP, MACE, FRCP(London); Chief Editor: Robert P Hoffman, MD  more...
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Answer

Postural testing is best performed after overnight recumbency. An IV catheter is inserted at 7 AM, and baseline aldosterone, cortisol, and PRA values are obtained at 8 AM. After 2 hours of ambulation, these values are obtained again.

Typically, APAs are unresponsive to angiotensin II, and a fall in aldosterone over 2 hours is observed in parallel with reduced circadian ACTH and cortisol release. In IHA, however, a rise in aldosterone is observed, during walking compared with lying down, because upright posture stimulates renin secretion. Cortisol levels are used to validate the test; a rise in cortisol release suggests an ACTH surge, which invalidates the test. Of note, 30–50% of APAs respond to upright posture and 20% of bilateral adrenal hyperplasia are unresponsive. A diagnostic accuracy of 85% is reported.


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