The Facts

Addison's disease, also know as primary adrenal insufficiency, is a rare condition that affects the body's hormonal activity. It is named after Dr. Thomas Addison, who discovered it in 1849.

Addison's disease occurs when the body is not able to make enough of the hormones cortisol and/or aldosterone. Each hormone works differently within the body. If either hormone is not present in sufficient amounts, there is an effect on many body systems. Blood pressure, the immune system, metabolism, sexual function, and insulin levels are just some of the body's duties that these hormones affect on a daily basis.

Causes

Addison's disease, also know as primary adrenal insufficiency, is caused by a problem within the adrenal glands themselves. Usually, this occurs when the immune system attacks the adrenal glands. Tuberculosis infection can also damage the adrenal glands.

A similar condition called secondary adrenal insufficiency occurs when the pituitary gland does not make enough adrenocorticotropin (ACTH), a hormone that stimulates the adrenal glands. This may be caused by pituitary tumours, brain surgery, reduced blood flow to the brain, or brain infections. It can also be caused by suddenly stopping corticosteroid medications after taking them for a prolonged period of time. In this case, the problem is usually temporary.

Symptoms and Complications

People with this condition may experience fatigue and muscle weakness. Other symptoms include:

• constipation
• darkened skin on exposed and unexposed areas of the body (also called hyperpigmentation) - this is a symptom of primary adrenal insufficiency
• diarrhea
• increased desire for salty foods
• lack of appetite
• low blood pressure (which may lead to fainting)
• nausea
• vomiting
• weight loss

Making the Diagnosis

Physical examination, a discussion of symptoms, and medical tests are the best way to determine if a person has Addison's disease.

Cortisol levels in the blood and urine help determine whether primary or secondary adrenal insufficiency is causing the condition. The ACTH test looks at the adrenal glands' ability to produce cortisol. Blood and urine samples are collected before and after an injection of synthetic (man-made) ACTH. This hormone stimulates cortisol production in healthy adrenal glands. Low or no cortisol in samples after the injection indicates Addison's disease caused by primary adrenal insufficiency.

Another helpful diagnostic tool is the corticotropin-releasing hormone (CRH) stimulation test. It uses a synthetic (man-made) version of the hormone CRH to see how ACTH responds and whether or not cortisol is produced. The release of CRH in the brain normally tells the pituitary gland to produce ACTH, which then stimulates the production of cortisol from the adrenal glands. The person receiving an injection of CRH and blood cortisol is monitored over a period of 2 hours. If CRH fails to stimulate the brain to produce ACTH, this indicates secondary adrenal insufficiency.

Other tests may include imaging technologies such as CT scan or MRI to get a better view of the adrenal glands or the parts of the brain (pituitary gland and hypothalamus) responsible for the release of specific hormones affecting the adrenal glands.

Treatment and Prevention

Hormone replacement therapy is the standard treatment for Addison's disease. Hormones that the body does not produce or that it produces in small amounts are replaced with a medication. Hydrocortisone is used to replace the missing hormone cortisol, and fludrocortisone is used to replace the missing hormone aldosterone. Because cortisol levels vary during the day, patients may require multiple doses of hydrocortisone every 24 hours. In normal individuals, cortisol levels rise in order to combat physical stresses such as infections. In people on steroid replacement, this is usually done by doubling the dose of the medication.

It is recommended that people with Addison's disease carry identification to let medical staff know of their condition. In the event of an Addisonian crisis where low blood pressure, low blood glucose, and high potassium levels may cause unconsciousness, identification alerts the medical staff to the need for cortisol and other special treatment.