[5][6] Symptoms generally come on slowly and insidiously and may include abdominal pain and gastrointestinal abnormalities, weakness, and weight loss.

[1] Under certain circumstances, an adrenal crisis may occur with low blood pressure, vomiting, lower back pain, and loss of consciousness.

[1] Addison's disease arises when the adrenal gland does not produce sufficient amounts of the steroid hormones cortisol and (sometimes) aldosterone.

[1] It is an autoimmune disease which affects some genetically predisposed people in whom the body's own immune system has started to target the adrenal glands.

[1] Lifelong, continuous steroid replacement therapy is required, with regular follow-up treatment and monitoring for other health problems which may occur.

[1] The disease is named after Thomas Addison, a graduate of the University of Edinburgh Medical School, who first described the condition in 1855.

Low blood cortisol can cause a variety of symptoms, including fatigue, malaise, muscle and joint pain, reduced appetite, weight loss, and increased sensitivity to cold.

[16] In women, low dehydroepiandrosterone (DHEA) can result in dry and itchy skin, loss of armpit and pubic hair, and reduced sexual drive.

[15] Low cortisol also interferes with adrenocorticotropic hormone (ACTH) regulation, sometimes resulting in the darkening of the skin and mucous membranes, particularly in areas exposed to sun or regular friction.

[15] The combination of Addison's disease in addition to mucocutaneous candidiasis, hypoparathyroidism, or both, is called autoimmune polyendocrine syndrome type 1.

Autoimmune adrenalitis is the most common cause of Addison's disease in the industrialized world as it represents between 68% and 94% of cases.

[6][21][22] Autoimmune destruction of the adrenal cortex is caused by an immune reaction against the enzyme 21-hydroxylase (a phenomenon first described in 1992).

[23] This may be isolated or in the context of autoimmune polyendocrine syndrome (APS type 1 or 2), in which other hormone-producing organs, such as the thyroid and pancreas, may also be affected.

[24] Adrenal destruction is also a feature of adrenoleukodystrophy, and when the adrenal glands are involved in metastasis (seeding of cancer cells from elsewhere in the body, especially lung), hemorrhage (e.g., in Waterhouse–Friderichsen syndrome or antiphospholipid syndrome), particular infections (tuberculosis, histoplasmosis, coccidioidomycosis), or the deposition of abnormal protein in amyloidosis.

Of the synthesis problems, congenital adrenal hyperplasia is the most common (in various forms: 21-hydroxylase, 17α-hydroxylase, 11β-hydroxylase and 3β-hydroxysteroid dehydrogenase), lipoid CAH due to deficiency of StAR and mitochondrial DNA mutations.

[12] Some medications interfere with steroid synthesis enzymes (e.g., ketoconazole), while others accelerate the normal breakdown of hormones by the liver (e.g., rifampicin, phenytoin).

[12] Routine laboratory investigations may show:[12] In suspected cases of Addison's disease, demonstration of low adrenal hormone levels even after appropriate stimulation (called the ACTH stimulation test or synacthen test) with synthetic pituitary ACTH hormone tetracosactide is needed for the diagnosis.

In primary Addison's disease, the cortisol level is reduced at all stages, whereas in secondary corticoadrenal insufficiency, a delayed but normal response is seen.

[28] Adrenoleukodystrophy, and the milder form, adrenomyeloneuropathy, cause adrenal insufficiency combined with neurological symptoms.

[31] People with Addison's disease are advised to increase their medication during periods of illness or when undergoing surgery or dental treatment.

[31] Immediate medical attention is needed when severe infections, vomiting, or diarrhea occur, as these conditions can precipitate an Addisonian crisis.

It may also be beneficial for the people with Addison's disease to increase their dietary intake of calcium and vitamin D. High dosages of corticosteroids are linked to osteoporosis so these may be necessary for bone health.

When the person is capable of swallowing fluids and medications by mouth, the amount of glucocorticoids is decreased until a maintenance dose is reached.

[40] About 70% of Addison's disease diagnoses occur due to autoimmune reactions, which cause damage to the adrenal cortex.

Because little was known at the time about the adrenal glands (then called "Supra-Renal Capsules"), Addison's monograph describing the condition was an isolated insight.

[57] In anticipation of stressful situations, such as staying in a boarding kennel, dogs require an increased dose of prednisone.