Conn's syndrome

Conn's syndrome is overproduction of the mineralocorticoid hormone aldosterone by the adrenal glands. Aldosterone causes sodium and water retention and potassium excretion in the kidneys, leading to arterial hypertension (high blood pressure). It is a rare but recognised cause of nonessential hypertension. It is named after Dr Jerome W. Conn (1907-1981), the American endocrinologist who first described the condition in 1955. It is the most common form of primary Hyperaldosteronism.

Signs, symptoms and findings

Apart from high blood pressure, the symptoms may include muscle cramps and headaches (due to the low potassium), metabolic alkalosis (due to increased secretion of H+ ions by the kidney). The high pH of the blood makes calcium less available to the tissues and causes symptoms of hypocalcemia (low calcium levels).

It can be mimicked by liquorice ingestion (glycyrrhizin) and Liddle syndrome.

Diagnosis

Measuring aldosterone alone is not considered adequate to diagnose Conn's syndrome. Rather, both renin and aldosterone are measured, and the ratio is diagnostic. Usually, renin levels are suppressed, leading to a very low renin-aldosterone ratio (<0.05). This test is confounded by antihypertensive drugs, which have to be stopped up to 6 weeks.

If there is biochemic proof of hyperaldosteronism, CT scanning can confirm the presence of an adrenal adenoma.

Causes

The syndrome is due to:

• adenoma (benign tumor, 50-60%)
• hyperplasia of the adrenal gland (40-50%)
• rare forms

Therapy

Surgical removal of the offending adrenal (adrenalectomy) takes away the source of the excess hormones. Meanwhile, the blood pressure can be controlled with spironolactone (a diuretic that counteracts the actions of aldosterone) and other antihypertensives.

Reference

• Conn JW, Louis LH. Primary aldosteronism: a new clinical entity. Trans Assoc Am Physicians 1955;68:215-31; discussion, 231-3. PMID 13299331.