Addison's disease overview

# Overview
Addison disease develops as a result of bilateral adrenal cortex destruction or dysfunction leading to reduced cortisol and aldosterone production. Autoimmune destruction of the adrenal glands is the most common cause in the western world, but hemorrhage, adrenal vein thrombosis, carcinoma and infections such as tuberculosis are also known significant causes. Tuberculosis remains the most common cause worldwide of Addison disease. The onset of Addison disease is often gradual, and symptoms of the disease can be difficult to recognize. It may go undetected until an illness or other stress precipitates adrenal crisis. Treatment should not be withheld to confirm the diagnosis. Treatment should be the priority, as the disease is fatal if it remains untreated. Diagnosis is made with rapid, high-dose adrenocorticotropic hormone (ACTH) stimulation testing. If the patient is hypovolemic, dexamethasone and intravenous normal saline should be given before stimulation testing is performed. The mainstay of therapy is a combination of glucocorticoids and mineralocorticoids. Glucocorticoid doses need to be doubled when patients have an episode of minor fever, infection, minor trauma, or minor physical stress. Intravenous stress-dose corticosteroids are needed for surgery involving general anesthesia and for major trauma.

# Historical Perspective
Addison's disease is named after Dr. Thomas Addison, a British physician who first described the condition in his paper "On the Constitutional and Local Effects of Disease of the Suprarenal Capsules" in 1855.

# Classification
Adrenal insufficiency disorders may be classified into two categories depending upon the duration of symptoms into acute or chronic forms, and based on etiology into primary or secondary adrenal insufficiency.

# Pathophysiology
The hypothalamus releases corticotropin-releasing hormone (CRH), which stimulates the pituitary gland to release corticotropin (ACTH). ACTH travels via the blood to the adrenal gland, where it stimulates the release of cortisol. Cortisol is secreted by the cortex of the adrenal gland from a region called the zona fasciculata in response to ACTH. Elevated levels of cortisol exert negative feedback on the pituitary, which decreases the amount of ACTH released from the pituitary gland. When the adrenal glands do not produce enough cortisol and aldosterone, it results in Addison's disease.

# Causes
Common causes of Addison's disease include autoimmune, tuberculosis, AIDS, CMV, hemorrhage, infarction, sarcoidosis and infections.

# Differentiating Addisons disease from other diseases
Addison's disease must be differentiated from other diseases that cause hypotension, skin pigmentation, and abdominal pain such as myopathies, celiac disease, Peutz-Jeghers syndrome, anorexia nervosa, syndrome of inappropriate antidiuretic hormone (SIADH), neurofibromatosis, porphyria cutanea tarda, salt-depletion nephritis and bronchogenic carcinoma.

# Epidemiology and Demographics
The prevalence of Addison's disease in the human population is estimated to be roughly 4-12 persons per 100,000 persons. The incidence of Addison's disease is approximately 0.6 per 100,000 individuals worldwide. Addison's disease can affect any age range. Addison's disease occurs more frequently in females, with a ratio of 12.3 to 1.

# Risk Factors
Common risk factors in the development of Addison's disease include other autoimmune diseases such as chronic thyroiditis, dermatitis herpetiformis, grave's disease, hypoparathyroidism, hypopituitarism, myasthenia gravis, pernicious anemia, testicular dysfunction, type I diabetes and vitiligo.

# Screening
According to American Endocrine Society clinical guidelines, there is insufficient evidence to recommend routine screening for Addison's disease.

# Natural History, Complications, and Prognosis
If left untreated, Addison's disease can be life-threatening. Complications of Addison's disease include hypoglycemia, addisonian crisis, hypoxia, hypovolemic shock, cardiac arrest, stroke. Prognosis is generally good in patients with Addison's disease as long as they are on life time hormone replacement therapy.

# Diagnosis

## History and Symptoms
Addison's disease often has an insidious onset. In many cases, the disease is only recognized when the patient presents with an acute crisis precipitated by a stressful illness or situation. Acute adrenal insufficiency should be considered in patients presenting with abdominal pain, nausea, diarrhea, hypotension, and fever. A detailed and thorough history is necessary. Specific areas of focus when obtaining a history from the patient of Addison's disease include recent changes in diet, any signs of postural hypotension and history of cancer or other autoimmune diseases, tuberculosis or any exposure to anyone who has been diagnosed with tuberculosis.

## Physical Examination
In many cases, Addison's disease is only recognized when the patient presents with an acute crisis precipitated by a stressful illness or situation. Acute adrenal insufficiency should be considered in patients presenting with abdominal pain, nausea, diarrhea, hypotension, and fever. Patients with acute Addison's disease usually appear dehydrated and lethargic. Physical examination of patients with Addison's disease is usually remarkable for hypotension, hyperpigmentation of the skin, and muscle weakness.

## Laboratory Findings
Diagnosis of Addison's disease is made by routine blood tests and specific tests. ACTH stimulation test is a specific test employed to determine the function of adrenal glands and to diagnose Addison's disease. The prominent finding of a rapid ACTH stimulation test includes failure of cortisol to rise in response to ACTH injection. Other routine laboratory tests employed include plasma cortisol level, serum ACTH level, plasma renin activity, aldosterone levels and serum biochemistry.

## Electrocardiogram
An ECG may be helpful in the diagnosis of Addison's disease. ECG findings in Addison's disease is due to hyperkalemia which include peak T waves and widened QRS complex.

## X-ray
An abdominal x-ray may be helpful in the diagnosis of Addison's disease. Findings on an abdominal x-ray suggestive of Addison's disease include adrenal calcifications.

## CT scan
There are no specific CT findings associated with Addisons's disease except for small adrenal remnants bilaterally and calcifications.

## MRI
There are no specific MRI findings associated with Addison's disease. While MRI is not capable of distinguishing between acute inflammatory and metastatic diseases of the adrenal glands, it may be equally efficacious as CT in suggesting the diagnosis of adrenal hemorrhage in patients with Addison's disease.

## Other Imaging Findings
There are no other imaging findings associated with Addison's disease.

## Other diagnostic studies
There are no other diagnostic studies associated with Addison's disease.

## Ultrasound
Abdominal ultrasound is typically normal in Addison's disease except for the small size of adrenal glands.

# Treatment

## Medical Therapy
The mainstay of treatment for Addison disease is corticosteroid replacement, if there is persistent mineralocorticoid deficiency, it should be combined with fludrocortisone.

## Surgery
Surgical intervention is not recommnended for the management of Addison's disease.

## Primary Prevention
There are no established measures for the primary prevention of Addison's disease.

## Secondary Prevention
Effective measures for the secondary prevention of Addison's disease include wearing an identification bracelet stating the name of the disease to ensure proper emergency treatment during an adrenal crisis. Patients diagnosed with Addison's disease and their family members should also be educated about risks of hormone replacement therapy and dose adjustments during periods of acute illnesses. Immediate medical attention must be given when severe infections, vomiting, or diarrhea occur.