Effect of posture on the plasma concentrations of aldosterone in hypertension and primary hyperaldosteronism.

Measurement of plasma aldosterone concentrations (PAC) at 8 a.m. and after 4 h in the upright posture can further assist in identifying the adrenal pathologic lesion in patients with primary aldosteronism. Increases in PAC are associated with hyperplasia, and decreases with adenoma. Normal increases in response to upright posture are observed in patients with essential hypertension with normal or reduced renin concentration.