Disorders of mineralocorticoid activity.

The investigation of syndromes of mineralocorticoid excess and deficiency has been reviewed. For screening for primary aldosteronism, repeated measures of plasma potassium on high sodium intake is the most practicable method. Further investigation should include saline infusion and, in cases of doubt, fludrocortisone/sodium loading. Differential diagnosis of adenoma from hyperplasia is best achieved by the aldosterone response to posture, CT scanning and, if necessary, adrenal venous catheterization. Suitable techniques for the investigation of secondary aldosteronism of unknown cause and for primary and secondary hypoaldosteronism are described, as well as the adjustment of dosage for replacement therapy where mineralocorticoid secretion is deficient.