Damage to the adrenal glands causes Addison's disease. These glands sit just above the kidneys. The adrenal glands are part of the system of glands and organs that makes hormones, also called the endocrine system. The adrenal glands make hormones that affect almost every organ and tissue in the body.
The adrenal glands are made up of two layers. The inner layer, called the medulla, makes hormones such as adrenaline. Those hormones control the body's response to stress. The outer layer, called the cortex, makes a group of hormones called corticosteroids. Corticosteroids include:
-
Glucocorticoids.These hormones include cortisol, and they affect the body's ability to turn food into energy. They also play a role in the immune system and help the body respond to stress.
-
Mineralocorticoids. These hormones include aldosterone. They balance the body's sodium and potassium to keep blood pressure in a healthy range.
-
Androgens. In all people, the adrenal glands make small amounts of these sex hormones. They cause male sexual development. And they affect muscle mass, body hair, sex drive, and a sense of well-being in all people.
Addison's disease also is known as primary adrenal insufficiency. A related condition is called secondary adrenal insufficiency. These conditions have different causes.
Addison's disease, also called primary adrenal insufficiency
This condition happens when the outer layer of the adrenal glands becomes damaged and can't make enough hormones. Most often, the damage is due to a disease in which the immune system attacks healthy tissues and organs by mistake. This is called an autoimmune disease. People with Addison's disease are more likely than are other people to have another autoimmune disease as well.
Other causes of Addison's disease can include:
- A serious infection called tuberculosis that mainly affects the lungs and also can destroy the adrenal glands.
- Other infections of the adrenal glands.
- Spread of cancer to the adrenal glands.
- Bleeding into the adrenal glands.
- A group of genetic conditions present at birth that affect the adrenal glands. This is called congenital adrenal hyperplasia.
- Medicines that block the body's ability to make glucocorticoid, such as ketoconazole (Ketozole), mitotane (Lysodren) and etomidate (Amidate). Or medicines that block the action of glucocorticoid in the body, such as mifepristone (Mifeprex, Korlym).
- Treatment for cancer with medicines called checkpoint inhibitors.
Secondary adrenal insufficiency
This type of adrenal insufficiency has many symptoms in common with Addison's disease. But it's more common than Addison's disease. Secondary adrenal insufficiency happens when the pituitary gland near the brain doesn't prompt the adrenal glands to make cortisol.
Typically, the pituitary gland makes a hormone called adrenocorticotropic hormone (ACTH). ACTH in turn causes the outer layer of the adrenal glands to make its hormones, including glucocorticoids and androgens. But with secondary adrenal insufficiency, too little ACTH causes the adrenal glands to make too little of these hormones.
Most symptoms of secondary adrenal insufficiency are like those of Addison's disease. But people with secondary adrenal insufficiency don't develop darkened skin. And they're less likely to have serious dehydration or low blood pressure. They're more likely to have low blood sugar.
Factors that can cause the pituitary gland to make too little ACTH include:
- Pituitary tumors that aren't cancer.
- Surgery or radiation therapy of the pituitary gland.
- Brain injury.
A short-term cause of secondary adrenal insufficiency can happen in people who suddenly stop taking medicines called corticosteroids. These medicines treat conditions such as asthma and arthritis. But stopping the medicine suddenly rather than tapering off can lead to secondary adrenal insufficiency.