Primary aldosteronism (al-DOS-tuh-ro-niz-um) is a hormonal disorder that leads to high blood pressure. It occurs when your adrenal glands produce too much of a hormone called aldosterone. Your adrenal glands produce a number of essential hormones, including aldosterone. Usually, aldosterone balances sodium and potassium in your blood. But too much of this hormone can cause you to lose potassium and retain sodium. That imbalance can cause your body to hold too much water, increasing your blood volume and blood pressure. Primary hyperaldosteronism has a number of causes. About 33% of cases are due to an adrenal adenoma that produces aldosterone, and 66% of cases are due to an enlargement of both adrenal glands. Other uncommon causes include adrenal cancer and an inherited disorder called familial hyperaldosteronism. Some recommend screening people with high blood pressure who are at increased risk, while others recommend screening all people with high blood pressure for the disease. Screening is usually done by measuring the aldosterone-to-renin ratio in the blood, with further testing used to confirm positive results. While low blood potassium is classically described in primary hyperaldosteronism, this is only present in about a quarter of people. To determine the underlying cause, medical imaging is carried out.