Primary hyperaldosteronism (Conn's syndrome)

Primary hyperaldosteronism is autonomous over-production of aldosterone by the adrenal glands — either from a single benign adenoma (Conn's syndrome) or from enlargement of both glands. Aldosterone tells the kidney to retain sodium and water and to excrete potassium, so too much of it raises blood pressure and can lower blood potassium. It is now recognised as the most common secondary (and potentially curable) cause of hypertension, present in perhaps 5–10% of people with high blood pressure and more in resistant cases — far more than the classic teaching suggested, partly because many people have normal potassium. Identifying it matters: the excess aldosterone damages the heart, kidneys and blood vessels beyond what the blood pressure alone would predict, and treatment — surgery for a one-sided adenoma, or a specific medication otherwise — can cure or greatly improve the hypertension.

• Potassium — may be low, but is often normal; a low potassium in a hypertensive patient is a strong clue.
• Aldosterone-to-renin ratio (ARR) — the screening test: high aldosterone with suppressed renin.
• Sodium — often high-normal.
• Confirmatory testing — saline-suppression or similar, done under specialist guidance.
• Adrenal CT and adrenal vein sampling — localise one-sided versus two-sided disease once biochemistry confirms.
• Blood pressure — often resistant to several drugs.

• Often none beyond the high blood pressure itself
• High blood pressure that is hard to control or starts young
• Symptoms of low potassium — muscle weakness, cramps, excessive urination, thirst
• Headache
• Tiredness Many people have no specific symptoms — it is found by screening the blood pressure.