Does the patient have hyperaldosteronism?
Spontaneous or diuretic-induced hypokalaemia has traditionally been considered a useful diagnostic guide for hyperaldosteronism in hypertensive patients. However, it has become apparent that up to 50% of subjects with primary hyperaldosteronism are normokalaemic (Gordon 1994). Moreover, the use of ACE inhibitors for hypertension elevates plasma potassium and might disguise underlying hyperaldosteronism. Therefore a high degree of clinical suspicion is required for diagnosis and hypokalaemia can no longer be considered a sufficiently sensitive diagnostic tool.
The use of random aldosterone/renin ratios as a first line test is becoming more established and is probably less affected by drug therapy, day and diurnal variation and patient position that either aldosterone or renin alone (McKenna et al 1991). The use of a ratio also helps to diagnose those subjects with early adenomatous hyperaldosteronism in whom the renin is suppressed but with a still "normal" plasma aldosterone concentration.
Once the diagnosis of primary hyperaldosteronism has been made, it then becomes necessary to establish the cause. The commonest cause will be an adrenal tumour and pre-operative localisation is necessary as tumours visualised on imaging are not always functional (see adrenal incidentaloma).
Causes of hyperaldosteronism
- Aldosterone producing adenoma,
- Idiopathic hyperaldosteronism,
- Glucocorticoid-suppressible hyperaldosteronism,
- Adrenal carcinoma.
Conditions mimicking clinical presentation of hyperaldosteronism
- SAME (Syndromes of apparent mineralocorticoid excess),
- Liquorice abuse,
- Cushing's syndrome,
- Congenital adrenal hyperplasia (11 beta or 17 alpha hydroxylase deficiency),
- Liddle's syndrome (mutation of beta subunit of epithelial sodium channel),
- Syndromes of cortisol resistance,
- DOC producing adrenal tumour.
- Gordon RD. Mineralocorticoid hypertension. Lancet 1994;344:240-243.
- McKenna TJ, Sequiera SJ, Heffernan A, Chambers J, Cunningham S. Diagnosis under random conditions of all disorders of the renin-aldosterone axis, including primary hyperaldosteronism. J Clin Endocrinol Metab 1991;73:952-957.
- Valloton MB. Primary hyperaldosteronism. Part I Diagnosis of primary hyperaldosteronism. Clin Endocrinol 1996;45:47-52.
- Valloton MB. Primary hyperaldosteronism. Part II Differential diagnosis of primary hyperaldosteronism and pseudoaldosteronism. Clin Endocrinol 1996;45:53-60.