Addison's Disease

Definition

Definition of Addison's Disease
Addison’s disease is a rare, chronic endocrine disorder in which the adrenal glands do not produce sufficient steroid hormones (glucocorticoids and often mineralocorticoids). It is characterised by a number of relatively nonspecific symptoms, such as abdominal pain and weakness, but under certain circumstances these may progress to Addisonian crisis, a severe illness in which there may be very low blood pressure and coma.

Symptoms

Symptoms of Addison's Disease
The symptoms of Addison's disease develop insidiously, and it may take some time to be recognised. The most common symptoms are fatigue, lightheadedness upon standing or while upright, muscle weakness, fever, weight loss, difficulty in standing up, anxiety, nausea, vomiting, diarrhea, headache, sweating, changes in mood and personality, and joint and muscle pains. Some have marked cravings for salt or salty foods due to the urinary losses of sodium. Increased tanning may be noted, particularly in sun-exposed areas, as well as darkening of the palmar creases, sites of friction, recent scars, the vermilion border of the lips, and genital skin. This is not encountered in secondary and tertiary hypoadrenalism.

Causes

Causes of Addison's Disease
Causes of adrenal insufficiency can be grouped by the way they cause the adrenals to produce insufficient cortisol. These are adrenal dysgenesis (the gland has not formed adequately during development), impaired steroidogenesis (the gland is present but is biochemically unable to produce cortisol) or adrenal destruction (disease processes leading to the gland being damaged).

Diagnosis

Diagnosis of Addison's Disease
In suspected cases of Addison's disease, one needs to demonstrate that adrenal hormone levels are low even after appropriate stimulation (called the ACTH stimulation test) with synthetic pituitary ACTH hormone tetracosactide. Two tests are performed, the short and the long test.

The short test compares blood cortisol levels before and after 250 micrograms of tetracosactide (IM/IV) is given. If, one hour later, plasma cortisol exceeds 170 nmol/L and has risen by at least 330 nmol/L to at least 690 nmol/L, adrenal failure is excluded. If the short test is abnormal, the long test is used to differentiate between primary adrenal insufficiency and secondary adrenocortical insufficiency.

The long test uses 1 mg tetracosactide (IM). Blood is taken 1, 4, 8, and 24 hours later. Normal plasma cortisol level should reach 1000 nmol/L by 4 hours. 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.

Treatment

Treatment of Addison's Disease
Treatment for Addison's disease involves replacing the missing cortisol, sometimes in the form of hydrocortisone tablets, or prednisone tablets in a dosing regimen that mimics the physiological concentrations of cortisol. Alternatively one quarter as much prednisolone may be used for equal glucocorticoid effect as hydrocortisone. Treatment must usually be continued for life. In addition, many patients require fludrocortisone as replacement for the missing aldosterone. Caution must be exercised when the person with Addison's disease becomes unwell with infection, has surgery or other trauma, or becomes pregnant. In such instances, their replacement glucocorticoids, whether in the form of hydrocortisone, prednisone, prednisolone, or other equivalent, often need to be increased. Inability to take oral medication may prompt hospital attendance to receive steroids intravenously. People with Addison's are often advised to carry information on them (e.g. in the form of a MedicAlert bracelet) for the attention of emergency medical services personnel who might need to attend to their needs.

Prognosis

Prognosis of Addison's Disease
A person with adrenal insufficiency should always carry identification stating their condition in case of an emergency. The card should alert emergency personnel about the need to inject 100 mg of cortisol if its bearer is found severely injured or unable to answer questions. The card should also include the doctor's name and telephone number and the name and telephone number of the nearest relative to be notified. When traveling, a needle, syringe, and an injectable form of cortisol should be carried for emergencies. A person with Addison's disease also should know how to increase medication during periods of stress or mild upper respiratory infections. Immediate medical attention is needed when severe infections, vomiting, or diarrhea occur, as these conditions can precipitate an Addisonian crisis. A patient who is vomiting may require injections of hydrocortisone, since oral hydrocortisone supplements cannot be adequately metabolised.

Prevention

Prevention of Addison's Disease
Consult with your doctor.