Addison's Disease

Exams and Tests

Addison's disease develops when the adrenal glands, located above the kidneys, are not able to produce enough of the hormones cortisol and aldosterone. Your doctor may suspect Addison's disease from your medical history, physical examination, and when blood tests show high potassium, low sodium, and high levels of certain types of white blood cells.

If your doctor suspects Addison's disease, you will have a blood test to determine your cortisol level.

Low blood cortisol levels do not always indicate Addison's disease. During a full day, cortisol levels are highest in the morning, drop during the afternoon, and are lowest overnight. Cortisol levels that are normal at one time of the day may be low at other times of the day. But the level of cortisol should be high when the body is physically or emotionally stressed. The diagnosis of Addison's disease is usually confirmed by doing an ACTH stimulation test, which helps show how your hormone levels react to stress. If your test results show you have high cortisol levels, when checked at random, or after the ACTH stimulation test, then you do not have adrenocortical disease.

• Low cortisol blood levels that fail to increase after an injection of ACTH indicate adrenal insufficiency.
• The levels of ACTH in the blood before an injection of ACTH indicate whether you have Addison's disease or secondary adrenocortical insufficiency, in which an inadequate amount of ACTH leads to low cortisol production. This may be caused by a problem with the pituitary gland, which controls hormone production.

X-rays, including computerized axial tomography (CAT scan) or magnetic resonance imaging (MRI), can also be used to check for damage to the adrenal glands.

If Addison's disease is diagnosed, your doctor will also look for thyroid problems, such as hyperthyroidism, hypothyroidism, and low production of parathyroid hormone, which causes a low calcium level in the blood. He or she will also look for other problems such as type 2 diabetes, pernicious anemia, and failure of the reproductive glands (testes and ovaries). One or more of these conditions are present in about one-half of those with Addison's disease.¹ It is especially important for people with Addison's disease to know if they also have thyroid disease. In people with low thyroid, cortisol lasts longer in the blood. Correcting a low level of thyroid hormone can lead to low cortisol levels and an adrenal crisis.

You may need to see an endocrinologist if the diagnosis or treatment of Addison's disease is uncertain.

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Author:	Caroline Rea, RN, BS, MS	Last Updated: February 20, 2008
Medical Review:	Caroline S. Rhoads, MD - Internal Medicine Alan C. Dalkin, MD - Endocrinology
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