Addison Disease

What is Addison disease?

Addison disease is an hormonal (endocrine) disorder involving destruction of the adrenal glands (small glands adjacent to the kidneys). In patients with Addison disease, the diseased glands can no longer produce sufficient adrenal hormones (specifically cortisol) necessary for the normal daily body functions. The disease is characterized by weight loss, muscle weakness, fatigue, low blood pressure, and sometimes darkening of the skin in both exposed and non-exposed parts of the body.

Addison disease affects about 1 in 100,000 people. It occurs in all age groups and afflicts men and women equally.
How does Addison disease occur?

Addison disease occurs when the adrenal glands do not produce enough of the hormone cortisol and, in some cases, the hormone aldosterone. For this reason, patients with Addisondisease are sometimes referred to as having adrenal insufficiency (or chronic adrenal insufficiency) or hypocortisolism (too little cortisol).

What is cortisol?

The hormone cortisol is normally produced by the adrenal glands. The adrenals are located just above the kidneys. Cortisol belongs to a class of hormones called glucocorticoids, which affect the normal function of almost every organ and tissue in the body. Cortisol's most important job is to help the body respond to stress. Among its other vital tasks, cortisol:

* helps maintain blood pressure and heart function;
* helps slow the immune system's inflammation response;
* helps balance the effects of insulin in breaking down sugar for energy; and
* helps regulate the metabolism of proteins, carbohydrates, and fats.

How is cortisol regulated?

Because cortisol is so vital to health, the amount of cortisol produced by the adrenals is precisely balanced. Like many other hormones, cortisol is regulated by control centers in the brain (hypothalamus and the pituitary gland, a bean-sized organ at the base of the brain).

First, the hypothalamus sends "releasing hormones" to the pituitary gland. The pituitary gland responds by secreting other hormones that regulate growth, thyroid and adrenal function, and sex hormones such as estrogen and testosterone.

One of the pituitary's main functions is to secrete ACTH (adrenocorticotropin), a hormone that stimulates the adrenal glands. When the adrenal glands receive the pituitary's ACTH signal, they respond by producing cortisol. Completing a "feedback" system, cortisol then signals the pituitary to lower secretion of ACTH.
What is aldosterone?

Aldosterone belongs to a class of hormones called mineralocorticoids, also produced by the adrenal glands. Aldosterone helps maintain blood pressure and water and salt balance in the body by helping the kidney retain sodium and excrete potassium. When aldosterone production falls too low, the kidneys are not able to regulate salt and water balance, causing blood volume and blood pressure to drop.

What causes Addison disease?

In patients with Addison disease, failure to produce adequate levels of cortisol (adrenal insufficiency) can occur for different reasons. Most cases of Addison disease are caused by the gradual destruction of the outer layer of the adrenal glands (adrenal cortex) by the body's own immune system. This form of Addison disease is, therefore, referred to as an autoimmune disease. The automimmune form of Addison disease can sometimes occur along with other autoimmune conditions, such as vitiligo, systemic lupus erythematosus, and Hashimoto's thyroiditis. About 70% of reported cases of Addison disease are due to autoimmune disorder, in which the immune system makes antibodies and immune cells that attack the body's own tissues or organs and slowly destroy them. Adrenal insufficiency occurs when at least 90% of the adrenal cortex has been destroyed. As a result, often both glucocorticoid and mineralocorticoid hormones are lacking. Sometimes only the adrenal gland is affected, as in idiopathic adrenal insufficiency.

Tuberculosis (TB) causes about 20% of cases of Addison disease in developed countries. When adrenal insufficiency was first identified by the English physician Thomas Addison in 1849, TB was found responsible in 70-90% of cases. As the treatment for TB improved, however, the incidence of adrenal insufficiency due to TB of the adrenal glands has greatly decreased.

Less common causes of Addison disease are chronic infections, mainly fungal infections; cancer cells spreading from other parts of the body to the adrenal glands; amyloidosis; surgical removal of the adrenal glands; bleeding in the adrenal glands; and sarcoidosis.
source:www.medicinenet.com