Conn syndrome

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Conn's syndrome is characterized by the 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 hypertension.

Signs, symptoms and findings
Conn's syndrome is also known as primary hyperaldosteronism. 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 (<0.0005). 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:
 * aldosterone-secreting adrenal 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.

Eponym
It is named after Dr Jerome W. Conn (1907-1994), the American endocrinologist who first described the condition in 1955.