Section 13. Hormonal Disorders

Chapter 164. Adrenal Gland Disorders

Topics: Introduction | Addison's Disease | Cushing's Syndrome | Virilization | Hyperaldosteronism | Pheochromocytoma

Hyperaldosteronism

In hyperaldosteronism, overproduction of aldosterone leads to fluid retention and increased blood pressure, weakness, and, rarely, periods of paralysis.

Aldosterone, a hormone produced and secreted by the adrenal glands, signals the kidneys to excrete less sodium and more potassium. Aldosterone production is regulated partly by corticotropin (secreted by the pituitary gland) and partly through the renin-angiotensin-aldosterone system (see Section 3, Chapter 22). Renin, an enzyme produced in the kidneys, controls the activation of the hormone angiotensin, which stimulates the adrenal glands to produce aldosterone.

Hyperaldosteronism can be caused by a tumor (usually a noncancerous adenoma) in the adrenal gland (a condition called Conn's syndrome), although sometimes both glands are involved and are overactive. Sometimes hyperaldosteronism is a response to certain diseases, such as very high blood pressure (hypertension) or narrowing of one of the arteries to the kidneys.

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Symptoms and Diagnosis

High aldosterone levels can lead to low potassium levels. Low potassium levels often produce no symptoms but may lead to weakness, tingling, muscle spasms, and periods of temporary paralysis. Some people become extremely thirsty and urinate frequently.

A doctor who suspects hyperaldosteronism first tests the levels of sodium and potassium in the blood. The doctor may also measure aldosterone levels. If they are high, spironolactone, a drug that blocks the action of aldosterone, may be given to see if the levels of sodium and potassium return to normal. In Conn's syndrome, the levels of renin are also very low.

When too much aldosterone is being produced, doctors examine the adrenal glands for a noncancerous tumor (adenoma). Computed tomography (CT) or magnetic resonance imaging (MRI) can be helpful, but sometimes blood samples from different parts of the body must be tested to localize the source of the hormone.

Treatment

If a tumor is found, it can usually be surgically removed. When the tumor is removed, blood pressure returns to normal, and other symptoms disappear about 70% of the time. If no tumor is found and both glands are overactive, partial removal of the adrenal glands may not control high blood pressure, and complete removal will produce Addison's disease, requiring treatment for life. However, spironolactone can usually control the symptoms, and drugs for high blood pressure are readily available. Rarely do both adrenal glands have to be removed.