The prevalence of Addison´s disease is estimated to be 1 in 100,000. Prevalence is the proportion of the population that suffer from a condition in a given period of time. 

Addison´s disease occurs in all age groups and it affects men and women equally.

Primary adrenal insufficiency or classic Addison´s disease is caused by the loss of the adrenal glands function. The most common cause is the destruction of the adrenal glands by an autoimmune reaction. The natural defenses of the body wrongfully detect the adrenal glands as an external threat and destroy them. It is estimated that 90% of the adrenal glands should be destroyed in order for the symptoms to appear.

Tuberculosis used to be the most common cause of Addison´s disease in the past, and it is still the case in developing countries.

Other more rare causes include the metastasis of cancer cells to the adrenal glands, chronic infections (mainly fungal), bleeding in the adrenal glands due to a trauma, amyloidosis (the accumulation of amyloid protein in the adrenal glands) or surgical removal of the glands.

Secondary adrenal insufficiency is caused by the lack of another hormone called adrenocoticotropic hormone (ACTH). ACTH is secreted by the pituitary gland in the brain and serves to indicate to the adrenal gland that cortisol needs to be produced. In this case, aldosterone is present. Secondary adrenal insufficency is considered a different medical entity than Addison´s disease.

The symptoms of Addison´s disease usually begin gradually and may worsen over time. The most characteristic symptoms are fatigue, unintended weight loss, and loss of appetite. Low blood pressure is common and can cause lightheadedness when standing and even fainting at times. It is also characteristic of the darkening of the skin (hyperpigmentation) in exposed and unexposed areas. Weakness of the muscles can also happen, and more rarely the muscles can suffer spasms (uncontrolled movement of the muscles). In some people nausea can happen, sometimes leading to vomiting. Diarrhea can also occur, but is more rare. Changes in the mood have also been described including depression, irritability, and loss of sexual appetite in women. A craving of salty foods is common, this is due to the loss of salts. Low blood sugar or hypoglycemia can also happen. In women, menstrual periods might become irregular or even stop.

The symptoms of acute adrenal insufficiency or addisonian crisis are more severe. They include severe pain in the lower back, abdomen or legs, pronounce vomiting and diarrhea potentially causing dehydratation, sudden loss of strenght, and low blood pressure that can cause loss of consciousness. An addisonian crisis is an emergency that needs immediate medical attention, the consequences can be fatal if left untreated. An acute adrenal insufficiency is usually triggered by an accident, trauma, surgery, or severe infection.

Diagnosis is sometimes difficult to obtain because most of the symptoms are not specific to Addison´s disease and can occur in other medical conditions. A detailed review of the medical history of the patient and the presence of characteristic findings (like the darkening of the skin) can point to Addison´s disease. In most cases, the diagnosis is made by clinical judgment during a routine exam when a regular blood test shows increased levels of potassium or reduced levels of sodium.

Biochemical testing can help confirm an Addison´s disease diagnosis.

The ACTH stimulation test can confirm a primary adrenal insufficiency. In this test, a synthetic version of the hormone ACTH is injected in the blood and the levels of cortisol are measured before and after the injection. If the levels of cortisol do not increase after the ACTH administration, it indicates that the adrenal glands are damaged and unable to produce hormones.

If the adrenal glands are able to respond and produce hormones after ACTH administration, an insulin-induced hypoglycemia test can be done to measure the pituitary gland function. In this case, a fast-acting insulin is administered and the levels of both cortisol and glucose are monitored in blood before and after its injection. Insulin should cause a drop in the levels of glucose and increased levels of cortisol. If this does not occur, a pituitary disease can be the cause of secondary adrenal insufficiency.

Sometimes, imaging test can be performed to check the size of the adrenal glands and to look for structural abnormalities in them. The most common technique is a computerized tomography (CT) scan. It is a special X-ray equipment that creates detailed pictures of organs or areas inside the body.

The treatment of Addison´s disease requires the administration of the hormones that the adrenal glands are not able to produce. This is known as hormone replacement therapy. Usually oral corticosteroids (hydrocortisone, prednisone or cortisone) are prescribed to replace cortisol. If vomiting is an issue, corticosteroid injections might be needed. The drug fludrocortisone replaces the hormone aldosterone. The dosage of these drugs is different in between different individuals and should be determined for each person. The dosage may be increase during events known to trigger an acute crisis like infection, trauma, surgery or other stressful situations. This is a long-life treatment that can not be abandoned.

An acute adrenal crisis requires the immediate injection in the blood stream (intravenous) of high-dose hydrocortisone and salt water to replace the lost salts. Sometimes other drugs to increase the blood pressure called vasopressors are required.

People with Addison´s disease can have a normal life provided that they continue to take their hormone replacement medication. There are no specific restrictions and the lifespan is not affected.

NADF. 2018. National Adrenal Disease Foundation. [ONLINE] Available at: http://www.nadf.us/adrenal-diseases/addisons-disease/. [Accessed 4 November 2018].

Eileen K. Corrigan. 2018. Pituitary Network Association. [ONLINE] Available at:https://pituitary.org/knowledge-base/disorders/adrenal-insuffieciency-addison-s-disease. [Accessed 4 November 2018].

Mayo Clinic. 2018. Mayo Clinic. [ONLINE] Available at: https://www.mayoclinic.org/diseases-conditions/addisons-disease/symptoms-causes/syc-20350293. [Accessed 4 November 2018].

NORD. 2018. National Organization for Rare Disorders. [ONLINE] Available at:https://rarediseases.org/rare-diseases/addisons-disease/. [Accessed 4 November 2018].