Conn's syndrome, or primary hyperaldosteronism, is a disorder caused by excess production of aldosterone, a hormone produced in the adrenal glands that helps control the amounts of sodium and potassium in the blood. Symptoms of Conn's syndrome include high blood pressure, headache, tiredness, excessive urination (often during the night), and a decrease in potassium levels in the blood.

Conn's syndrome is often caused by an aldosterone-producing tumour on the adrenal gland. Other times the adrenal glands start making too much aldosterone. It is not known why this happens.

If the tumour causing Conn's syndrome can be found, it is removed through surgery. If high blood pressure continues after surgery, or if surgery is not done, treatment may include medicines to block aldosterone, a diet low in salt, or both.