If you have high blood pressure that is difficult to control, this test can help find the cause. The Aldosterone, Serum test measures the level of a powerful hormone produced by your adrenal glands that regulates your body's salt and water balance. High levels can cause your body to retain salt, driving up blood pressure. This test is essential for diagnosing primary aldosteronism (Conn's syndrome). This simple blood test is a critical, specialized tool that moves beyond treating symptoms to find the root cause of your hypertension.