What causes Adrenal Insufficiency and Addison's Disease ? 

Autoimmune disorders cause most cases of Addisons disease. Infections and medications may also cause the disease.
                
Autoimmune Disorders
                
Up to 80 percent of Addisons disease cases are caused by an autoimmune disorder, which is when the bodys immune system attacks the bodys own cells and organs.2 In autoimmune Addisons, which mainly occurs in middle-aged females, the immune system gradually destroys the adrenal cortexthe outer layer of the adrenal glands.2
                
Primary adrenal insufficiency occurs when at least 90 percent of the adrenal cortex has been destroyed.1 As a result, both cortisol and aldosterone are often lacking. Sometimes only the adrenal glands are affected. Sometimes other endocrine glands are affected as well, as in polyendocrine deficiency syndrome.
                
Polyendocrine deficiency syndrome is classified into type 1 and type 2. Type 1 is inherited and occurs in children. In addition to adrenal insufficiency, these children may have
                
- underactive parathyroid glands, which are four pea-sized glands located on or near the thyroid gland in the neck; they produce a hormone that helps maintain the correct balance of calcium in the body.   - slow sexual development.   - pernicious anemia, a severe type of anemia; anemia is a condition in which red blood cells are fewer than normal, which means less oxygen is carried to the bodys cells. With most types of anemia, red blood cells are smaller than normal; however, in pernicious anemia, the cells are bigger than normal.   - chronic fungal infections.   - chronic hepatitis, a liver disease.
                
Researchers think type 2, which is sometimes called Schmidts syndrome, is also inherited. Type 2 usually affects young adults and may include
                
- an underactive thyroid gland, which produces hormones that regulate metabolism   - slow sexual development   - diabetes, in which a person has high blood glucose, also called high blood sugar or hyperglycemia   - vitiligo, a loss of pigment on areas of the skin
                
Infections
                
Tuberculosis (TB), an infection that can destroy the adrenal glands, accounts for 10 to 15 percent of Addisons disease cases in developed countries.1 When primary adrenal insufficiency was first identified by Dr. Thomas Addison in 1849, TB was the most common cause of the disease. As TB treatment improved, the incidence of Addisons disease due to TB of the adrenal glands greatly decreased. However, recent reports show an increase in Addisons disease from infections such as TB and cytomegalovirus. Cytomegalovirus is a common virus that does not cause symptoms in healthy people; however, it does affect babies in the womb and people who have a weakened immune systemmostly due to HIV/AIDS.2 Other bacterial infections, such as Neisseria meningitidis, which is a cause of meningitis, and fungal infections can also lead to Addisons disease.
                
Other Causes
                
Less common causes of Addisons disease are
                
- cancer cells in the adrenal glands   - amyloidosis, a serious, though rare, group of diseases that occurs when abnormal proteins, called amyloids, build up in the blood and are deposited in tissues and organs   - surgical removal of the adrenal glands   - bleeding into the adrenal glands   - genetic defects including abnormal adrenal gland development, an inability of the adrenal glands to respond to ACTH, or a defect in adrenal hormone production   - medication-related causes, such as from anti-fungal medications and the anesthetic etomidate, which may be used when a person undergoes an emergency intubationthe placement of a flexible, plastic tube through the mouth and into the trachea, or windpipe, to assist with breathing
                

                
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